First thing I'd do is go over to Newegg.com and compare their prices with Micro Center's. Going to the various hardware categories and choosing the "Top Sellers" search option generally turns up items that are the best bang for the buck, and the user reviews are generally pretty good.
If you're running a bunch of VMs and want to keep the CPU cost < $200, consider the Intel Q6600, which is what I use. $189 and free shipping. Of course, now that I look at MC's site, I see they have the Q9300 for $179.99 - this is an excellent deal, even after adding in your local sales tax.
Memory has a ridiculous number of options. If you're concerned about CAS latency and timing, the
CORSAIR XMS2 DHX 4GB (2 x 2GB) option (CAS:4, Timing 4-4-4-12) looks good for $39 after mail in rebate.
Motherboards are even more up to you. I've had good luck with DFI and Gigabyte mobos in the past, but now I focus more on the features, cost, and user reviews.