Best speakers for $300/pr

$300 can go a very long way on the used market.  It depends on his listening preferences (rock, classical, jazz), room size, how powerful the Marantz is and if he wants monitors or floor standing speakers.  Too many variations to start mentioning brands at this point until the above is known.  

Once the above is known then you can tailor his needs towards a certain sound from speaker manufacturers.  British 2 way monitors have a certain sound to them, sweet and disappearing, that I tend to like very much but may not be for everyone depending on their musical tastes.  

Please keep us posted,
Lou

I have disappointing news.  His “mid-fi” mentality has been revealed.
After hearing one of the very well touted speakers recommended here,
he found the violin sound not as mellifluous as his KLH speakers (he’s mainly  a classical music listener.)
So I think he’s sticking with the KLH.

You can lead a horse to water....

Thanks for all the suggestions though.  I had no idea good sound could be achieved in that price range.

 

I will second the spica t-50 s with a sub woofer

Check out Philharmonic Audio outstanding sound at reasonable prices. They have an Accuracy Monitor for $290.00

The problem is you get used to a certain sound and even if you hear something superior, you don't always realize it when you hear it.  Having been in this hobby for 30 years, I believe we all have an aural memory such as I've described above.  That is why when I make any change in my system, I like to live with the different gear so that the new sound grows on me.