Corsair or PC Power & Cooling PSUs are great.
For 3D work, stay away from regular video cards. TomsHardware just released an article testing the much more powerful GTS 280 against Workstation cards. The $150 ATI V3600 smokes the GTS 280. You can save a lot of money and get a 775 based setup with the Q8300 + ASUS P5Q Pro ($300 or less in US for this combo). The most significant impact on performance will be the Video card. If you can get your hands on a Nvidia 8800GTS 640MB, you can "Soft-mod" it to a FX4600. The 8800GTS is a little older but can provide the largest performance increase per Dollar. Or the ATI V5600($350 US) is very competent too.
For the CPU, you can easily overclock the Q8300 from 2.5GHz to 3.2GHz, which is faster than the i7 920 at its stock 2.66GHz. Most rendering is done overnight, so a 5-10% reduction in rendering times is not really worth an extra $300-400. Take that extra $300 and put it towards a Workstation card which will provide a real-time performance increase while working in 3D programs.
Take a look at these 2 articles and the pages that come up in the links:
http://www.tomshardware.com/reviews/quadro-fx-4800,2258-10.html
http://www.tomshardware.com/reviews/amd-firepro-v8700,2154-10.html
The ATI 4870 is more powerful in 3D programs than the GTS 280. Look for this comment in the ATI FirePro article,
"We also decided to investigate if there were visible differences in picture quality between the two models. On a basic Windows desktop we discovered no discrepancies, but as soon as you load a professional graphics application such as Maya or 3ds Max and import a complex 3D model, things change completely. When using the Radeon, you simply have to accept that wire frames will peek out of shaded surfaces all over the place, and that significant clipping occurs as numerous objects are viewed or animated. These phenomena simply don't occur when using the FirePro. Bottom line: those who seek to be frugal with expensive workstation applications should not fall prey to false economies. "