I just built my dream machine (i7 6-core + Cintiq + lots of disk) and love it. I got almost everything from NewEgg and got a lot of advice from the people in the forums at tomshardware.com.

If you're not interested in building your own, then I would suggest Boxx (http://www.boxxtech.com). They build nice computers at a reasonable price, from single-user machines to full-on render farms. And no, I'm not affiliated with them at all.

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D. Jay Newman