I use these guys:
http://www.magicmicro.com/I've bought two computers from them - 1 like 4 years ago and one in Feb. I couldn't be happier with the service and have told everyone that will listen how awesome they are.
You can start with a barebones kit and then add/customize whatever you need, keep the parts you don't want to replace (for instance, i'm still using my old HD with my old windows installation because i had purchased it less than a year ago).. best of all they put all the parts together before it leaves and you get all the components you picked ready to plug in, or just ready to add the HD to in my case. What i did was basically look up each component they offered on Newegg, got the customer service rating from there, (reliability, DOA, etc info) and picked each part based on that info.
The customer service absolutely cannot be rivaled. On the machine i bought 4 years ago, i decided to upgrade the vid card because i wanted more performance out of wow. I had lost my original invoice and wasn't sure what would be compatible (being lazy and not wanting to open the case) - so i e-mailed them asking if they could help at all. Not only did they reply within 24 hours they gave me a list of exactly what cards would work. Mind you this was 2 years after the initial purchase and i didn't purchase any sort of warranty.
You can customize
literally everything right down to the case. There is no fee for the assembly and they are lightening fast - the system that i ordered in February was shipped within 48 hours of the initial order.
I love these guys and i don't think i'll ever buy another computer from anywhere else, ever.
