$600 will buy a good custom wheelset. You can get CXP-33 or Open Pro rims with 105 or similar quality hubs for much less than $600. I'd definitely suggest you go the custom route. Aside from Psimet, there is also Bicycle Wheel Warehouse and Wheelbuilder.com. My current wheels (CXP-33 rims / Dura-Ace hubs) came from BWW and I cannot overstate how happy I am with them. I've also purchased wheels from Psimet, but they are yet to show up so the jury's still out on those....