If you go the DIY route then maybe something like this
CPU: Intel Core i7-3770 $299.99 (
Link)
MB: MSI Z77MA-G45 LGA 1155 $109.99 (
Link)
RAM: CORSAIR Vengeance 16GB (4 x 4GB) $73.99 (
Link)
SSD: OCZ Agility 4 2.5" 64GB $59.99 (
Link)
PSU: Rosewill Green Series RG630-S12 630W $49.99 (
Link)
Case: Rosewill CHALLENGER Black Gaming ATX Mid Tower $49.99 (
Link)
Total (Before Shipping)
$643.94 / After Rebates:
$633.94
Optional
GPU: GIGABYTE GV-N630-1GI GeForce GT 630 1GB $59.99 (
Link)
Operating System: Linux is FREE / Windows 7 HP $99.99 (
Link)
If you shop around you might find better prices but Newegg has everything you need. And don't forget to shop through
Fat Wallet or
eBates to get another 4% or 5% off your total.