Our home computer just died and we searched for a replacement that would stand up to high demands and last a few years. After much searching, we ended up with a Tigerdirect.com refurbshed unit:
Asus Essentio CG5275-AR003 Refurbished Desktop PC - Intel Core i5 650 3.2GHz, 8GB DDR3, 1TB HDD, DVDRW, Windows 7 Home Premium 64-bit at TigerDirect.com
It seems like a really good deal. My wife tried to pay more to get a higher end unit that would last longer but the guy who sold it said this was the best one for the price and not to spend more. It's far better than what the computer vendor I use for my firm had to offer for at least $400 less.
I'd look over Tiger Direct and compare their specs and prices to new and used with other companies.