Some guidance please?

Don't buy speakers at all. They just clutter up your listening room and cause you to buy all that expensive speaker wire from the wire bandits. Little kids always push in the tweeters and the cat is attracted to the grills. Skip the speakers altogether and spend the money you are saving on a better receiver.

Viridian, you seem like quite the witty character. I was about to dismiss your advice until I read some of your feedback. You're obviously a knowledgeable audio enthusiast(and a bit of a comedian). I always thought Denon made very good receivers. Why do you think differently? Any speaker would be completely safe in my house. I prefer dogs to cats and at 31, I know better than to push the tweeters in.(my girlfriend keeps asking me if I'm ever going to grow up!)

Guilty on all counts! I would caution you that there is quite a bit of folderol on this site, though it must be less than on some others. If you doubt this check the chat section and click on "disputes". Audiogon stopped airing these openly about a year ago, but you will get the idea. Many center around the misgrading of gear but there are a lot of diputes regarding shipping damage as well. Which brings me to my next point. After turntables, speakers are the most likely items IMHO to suffer shipping damage. Go into shipping speakers eyes wide open, and deal with someone who is very familiar with shipping speakers. Double boxing can be a not inexpensive, but valuble option that I ususally require.

That said, there are many good speakers out there. Modern computer analysis and modeling has become a valuble tool that has really helped modern designers to deliver an incredible product at very modest prices. The best advice is to get out and listen to find out what your taste is. That said, I like the speakers designed in Canada with the help of the NRC; any time a government wants to pay for loudspeaker research that works just fine for me. The Paradigm and PSB brands are just great. Easy for your Denon to drive with robust sound, they make a lot of nice models to choose from as well. They tend to be well regarded and plentiful on the used market. Check out their websites. The Denon is a marvelous receiver; I was just being crass, as ususal. Viva la cats.
Marty

As usual you're getting some good advice here. I second the Canadian speaker recommendation. PSB, Paradigm, Pinnacle (I don't know why they all start with P - it's a Canadian thing eh?) - all excellent values that you can drive easily with the receiver you have.
Now - Size - yes size matters, but in different ways than you might think (ask your girlfriend and push in her tweeters while you're at it) No you're not ever going to grow up - get over it already.
Large speakers usually mean better bass, while smaller, stand mounted speakers usually have better imaging. You already have a sub, so maybe smaller speakers (called monitors) could be your thing. They take up less floor space, are less obtrusive looking and often are better for music.
PSB used to have the Stratus Mini, which was superb - you could get two of those, a C6i center and some Alpha's for the rear and be way under $2k, and have a great sounding system to boot. Oh, and they're easier to ship. 100lbs of speaker costs a fair sum to ship.
Put some $ into decent cable, and you're ready to go.
have to agree about Polks - not a bad speaker but sinks about as fast as Big Pussy on the Sopranos price wise - as does Definitive Technology, which might be something to consider for a real theater speaker - flabby uncontrolled self powered built-in subs - dreadful for music, but fine for your next blow-em-up action film.

If you do decide to plunge into the used market for speakers, you might also want to consider trying to go for local pickup. It beats the heck out of shipping damage, you get to see them just before you hand over your cold hard cash (not that there have ever been grading disputes here ;~), and you know they didn't get thrown off the truck at the end of your driveway.

I've been very lucky in my limited experience - shipped speakers arrived just fine, and driving to pick up some other (and larger) pairs worked wonderfully, too (though I'm still paranoid about the shipping and figure it's just a matter of time until the luck runs out). And the best part about pickup? I've met a couple of the absolutely finest class acts you could ever imagine - worth the trip! (And I agree w/ those Paradigm, PSB, etc. comments, too - they can be a great combo w/ a 3805). Good luck!