Best "Bookshelves" for $500? new or used

About two months ago I got a pair of B&W 601 series 2 for $500 to go w/ my used, budget "mid-fi" system: 1)Rotel RB-980BX amp (120W), 2)Rotel RC-972 pre-amp, 3)DIY TNT-audio X 1.5 IC's (12 strand,30 GA silver-coated OFC), and 4)bi-wired Chris Venhaus DIY (27 pair braid) Cat 5 teflon speaker cables. Originally, I used a Denon 360 carousel w/ Alpha processor (5 cdp for girlfriend) as my source, but found the highs to be really agressive at times (sibilance?). So, I switched to the Denon 370 carousel w/ Burr Brown's. Beautifully warm and smooth unit initially that is oh-so silky, but after a few days I realized that it seriously lacked detail, highs rolled off, and made mid-bass boomy. So I think I'll get a used MSB Link DAC 1 (upgrade later) and a decent 5 disc transport. Anyway, after breaking in, the B&W's seemed like a great buy, but now I'm beginning to think that high freq trouble may be a result of their tweeter and maybe they aren't as engaging as they should be. Possibly because B&W really meant these for home theater. Now I am looking for something w/ better soundstage, imaging, and presense. I now this is a tall order for $500 (used), but something that will fill my room with a detailed, spacious, engaging sound. Preferably bi-wirable now that I spent a month making the cables. I've read great things about the Paradigm Atoms for $200 new, but maybe these are the new budget flavor of the year. Any suggestions? Feel free to email me. Victor