I keep rebuilding this thing, which I know is futile; prices can change at any time. Oh well, it keeps me occupied. It also turns out that he edits video far less than I had thought. Current plan:
CPU/Mobo (181.98) - AMD Athlon II x4 640, Gigabyte GA-870A-UD3
RAM (34.99 after rebate and coupon) - Corsair 4GB (2x2GB) DDR3 1333 9-9-9-24
GPU (34.99 after rebate) - Sapphire Radeon HD 4650 1GB
HDD/PSU (111.98 after rebate) - Samsung Spinpoint F3 7200RPM 1TB, Corsair Enthusiast Series 650W
ODD (17.99) - Lite-On 24x DVD Burner
Case (49.99) - Rosewill Destroyer
OS (99.99) - Windows 7 Home Premium 64-bit OEM
After Rebates: 545.61
If he's willing to spend more to improve his video editing, I'm thinking of suggesting a second HDD (54.99, Samsung Spinpoint F3 7200RPM 1TB) for page file and additional storage as well as a bump to 8GB RAM (74.99 after rebate, Corsair 8GB (2x4GB) DDR3 1333 9-9-9-24). This would bring the after-rebate total to 641.86.
How much difference would the upgrades really make?