What speaker suit Yamaha RX-V2400?

You really should get the speakers, and then match the amp!
What most do, like you're going, is backwards (I speak from 15 years and 6 audio stores worth of experience, and then some).
Many, such as yourself, get to attached to gear, and then think of the speakers as after-thoughts!
Get the speakers that work the best for your needs, room, budget, set up, etc. Then, match an amp/pre and source, then cabling, line conditioning, tweaks, whatever....my suggestion.
The RXV2400 is a bit dull when you engage the EQ parameter into the mix, so beware. That said, the Yamaha's are "usually" a bit hollow in the mid, slightly cool, dynamically a tad lean, and somewhat agressive on top(sometimes bright), compared to other traditionally warm sounding more full bodied receivers in that price range(like Denon). If you are indeed staying with the 2400, and don't want to look at other routs (I strongly recommend Outlaw Separates, which destroys your receiver sonically).
But then it's relative to your speakers characteristics ultimately.
I've liked Yamaha's neat DSP modes, which were generally much better than others. Also, as a pre/pro, the Yamaha's where generally clean, detailed, and uncolored, and sounded infinitely better when you added an outboard amp to them!
Still, on it's own, at the very least, the amp section will hold back any real potential sonic quality. That, and I've yet to hear any receiver's Parametric or "automatic" EQ work so well ultimately, in regards to improving sonics!. It seems the sound (digitally) becomes too processed in the mid and upper(in the case of the Yamaha, tamming "air" and "extension" in the treble).
Back to your question; I would mate speakers that are a bit warm and fat(although you can make a fatter bass-heavy sound by placing the speakers and seats for better bass coupling), and maybe more foreward. Speakers like Klipsh's come to mind. Maybe you'd like the Polk's, which are often warm. When using the EQ on your 2400, you might also find the polks brightness uptop to mate oK.(some).
Still, I remember that the bigger floor standing, VERY EFFICIENT AND SENSITIVE KLipsch SB or Ref series speakers you buy at "Best Buy" or "Goodguy's" and such should do well with your limited powered receiver sonically. I think you might check this out if you are staying with you're receiver. The limited power your receiver has current-wise will be more than made up for with the easy to drive Klipsh's.
If you are going with more pristine, delicate, even audiphile speakers out there, with lower sensitivity, I'd suggest a minimum of Denon, but strongly considering separates, like I suggested! OTherwise, YOu're ok with the likes of the more highly touted B&W's, or Paradigms I supose.
good luck

Wow thanks for your response Exertfluffer !

First point - choose the speakers first - how do u do that - when u go to audition the speakers they are always powered by something? and therefore coloured by what its driven by. Thats why I thought choose your amp and then match the speakers to it - but hey I am a novice so what do I know - that why I ask the questions.

The room that this gear is going into isnt huge - 5m x 5m. I already have a 2channel Yamaha amp RX-596 with two very efficient Cerwin Vega E712 floorstanders and a B&W ASW1000 subwoofer. Sounds fine to my ears. But now its time to go to home theatre however these speakers also need to do music in fact in all fairness the duties will be split probably 70& music 30% home theatre - so the speakers will really need to perfom musically as well as for movies.

You mentioned Klipsch, B&W (that could be good as I already have the sub) and Paradigms - are these pretty much of a much between them or would one likely stand out as better than the others? What sort of prices are they going for?

Thanks for your advice in advance I really appreciate it.

Allan

No problem.
Well certainly syset matching is very important, as is room set up, acoustics, calibration, etc. IF you heard a system set up somewhere that you really liked, then you know the posssible potential there. In that case, you might try that combination you heard, but beware that each room is different, and requires different considerations often.
Getting it back to your "acoustically differnt" home and set up will give different restults, so consider.
Still, an easy way to match is to bring home just the left and right speakers(get em set up right first however, where they give good imaging and "Flat response") and try with the amp you think you want. Then you'll have a better idea of the sound. You can then pick up other speaker
Actually what speakers you should ultimately choose depends on a few criterion. For one, how tall is your ceiling? How far back do you intend (is it flexible?) from your main speakers? What are the acoustics of your room (i.e, surfaces, ceiling texture/shape), furniture in the room/stuff on the walls, etc)?
This can all have a great effect on sound, and certain speakers will ultimately work best depending.
For instance, if you sit way back towards the back, and you have a low flat ceiling with no acoustic treatment, then more "controled focus" (like Klipsch horns, or Dappolito configured speakers) speakers, which allow less ceiling and floor interaction with the sound you hear directly) speakers are for you. If you sit closer to your speakers(often recommended, depending), hearing more "direct sound" than reflected sound mixed with the main signal proportionately, You can use the more traditional "tweeter over mid/woofer" configured typical speakers, like B&W and Paradigm traditionally sell.
Still, I remember that the big floor standing Klipsch's just tend to sound a bit warmer, which matches with the Yamaha's better in my recollection. Although the MOnitor series from Paradigm will probably work ok there too...but I lean towards K's for your RXV2400 choice.
If you can choose other receiver, you have more flexibilty IMO. In the end, it depends on taste however.
So, in responding to your statement about the gear coloring the sound of the speakers, that's true. Still, the speakers have a much greater impact on the coloration and tonality of the sound on their own, than any associated equipment! This is more true of midfi gear as opposed to higher-end speakers that tend to be more neutral and transparent however. Still, the speaker are 60% of the sound of the gear. So chose that first.
You can have great sounding speakers, and still get descent sound with not so great associated gear. But if your speakers aren't so good, no amp in the world will make em sound good!!! So make sure you like the speakers in your room/set up, then match accordingly.
Ultimately, if you are trying to get "the best you can find", then you need to do "trial and error" if you're doing it on your own, as tastes will vary (that's why everyone has differnt gear). Otherwise, you pay someone to put it all together for you. IF not, you do what every other audiophle tweak does, and that's try one thing at a time, and try differnt stuff/changes, until you get what you like! There's no "quick solution" to sonic nirvana....sorry.
If you simply want to find some speakers that go with your amp your getting, then try and see, until you find the speakers you like. Then, you can always try another amp or option there if you want to upgrade further. Tinker, tinker, tinker, is the only way to improve if you want to keep improving sound. Otherwise, go find a speaker system you like, and then try amp's with it. Good luck