Best floorstanding speakers less than $500

the canton gles are surprisingly good full range floorstanders--fo to accessories4less. older energ--audissey or c series--are also good at your price point.

Normally, I'd recommend a very efficient, or voltage-loving speaker on stands.
You always have to make trade offs at your price point. Since your amp uses negative feedback and, thus, has good damping ability, I suggest a speaker whose main fault is flabby woofers.
However, the Wharfedale Diamond 9.6's are efficent and present an easly load.
And, since they're 4-way (to help efficiency, probably), the woofer's are, I'm guessing, relatively, flabby (hey, four drivers--you get what you pay for).
So, from a technical stand point, they should, probably, work.
However, will you like the resultant sound? I have no idea.

I suppose I should say I listen to rock and folk, and prefer a slightly more "bright" and forward sound (rather than a subdued clinical sound). But I also like accuracy, too. I understand that I'm asking a lot for speaker recommendations, but I just want to make sure I'm getting the best bang for the buck. I can always sell whatever I buy and try other stuff. And at this price am I just plain old better off going with bookshelves?

Uncledavid,
Bright, forward, accurate, rock, under $500......used Klipsch, probably Cornwall.

Don't sweat it. You can get that sound by choosing the right tubes for your amp. Go new Chinese or Russian, or NOS Amperex A-frames, or, maybe NOS German/Siemens and their ilk.
You, already, have an an amp that's not warm. It's "neutral". So, it shouldn't be very hard.
For example, new, reissued Tung Sols, etc.
Ask Kevin Deal at Upscale Audio. He'll set you up right.