My E6400 at stock speeds, 4gb DDR2, 2x250gb Maxtors, 1 500gb Seagate, 88000 GTS 640mb, SB X-FI, USB PCI card, 2 120mm fans, 2 80mm fans, PCI fan, DVD drive, a few USB devices.
Runs about 260W (taken via the Kill-A-Watt) at 80-100% load on both cores and a good load on the video card. I run a 600W PSU, but a lot of what I need in needed on the amperage of the 12V rail.
When I listed that Thermaltake, I really didn't take a close look at the power requirements for the 3850. I would go with Skuzzy on the PSU concerns.
On the RAM note, the E8400 runs at quad pumped FSB at 1333mhz. Essentially it's 333mhz (quad pumped). So to maintain a 1:1 ratio of FSB:RAM, DDR2 needs to be at least 667mhz (2x333mhz), or PC5300. So PC6400 at 800mhz (2x400mhz) would more than do the job at stock speeds. Overclocking...is a whole different ball game.