Best speakers under $500? Fire away!

Another vote for JBL Studio 530. Compression driver is super smooth. 

The NAD 3020 is only 20 watts, but has a really stiff power supply.  It ... might ... be OK with Elacs.  I'd definitely have the soft clipping feature turned on, though.

I'll second the post for Paradigm 20 or 40 Studio v's. They fade next to XR50's and 100's but are still sweet and (used) are easily in this range.

If you can find a pair of Spica TC-50s (with stands) or a gently used pair of Magnapan MMG's (new they're only $599), you might be surprised at how musical and how accurate they both are.

Gallo Acoustics still has some Classico CL-2 in stock. They were originally 1200 through dealers, then 800 direct. I just bought a pair for $390. A friend brought over his Elac B6 for comparison. The Gallos, as expected, completely outclassed them so he bought a pair of CL-2. Awesome speaker for that price.