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.

The Wharfedales are very nice for the money.TSTO sells the 9.4 for $299.They also sell the Mordaunt Short MS-914 for less than $400.I have the 902 bookshelf version (in my wife's sitting room) and they look and sound great! The MS speakers do feature a bright,clear sound from their metal dome tweeters.

Whose TSTO?

It's now TSO Sound and Vision.Used to be The Stereo Trading Outlet(in Jenkintown,PA)

Check out the Energy speakers at less then 1/2 off and free shipping, these might fit your bill:

http://www.vanns.com/shop/servlet/item/reviews/542061916/energy-rc30-cherry

Thanks for the great input guys. For the price the Wharfedales look to be the best bang for the buck as far as I can tell. I'm still not sure if I'm better off with a bookshelf for the price. Any thoughts? Also the energys look great but are beyond my price range currently.

Check out the JBL E50 bookshelfs,or if you can score used pair of the older S38 model.Both modells are very good for rock and they will be good match for the Onix.Good luck.

Uncledavid,

I have used the 9.6 Wharfedales with the Onix SP3 and it is a really nice combination. I moved the system to the bedroom and am now using the 9.2's and I'm very satisfied. With that system I'm using Anti-Cables with excellent results. I say if you have room for the 9.6's to go for it.

Used Triangles go for insane prices.

I think a Vadersteen 1 would give you very good performance with decent bass extension.