I'm trying to choose a PSU that will give me some expansion room. What amps on the 12v will I need for either of these builds:

1) PII XE 720 overclocked to 3.6ghz, two Radeon 4850 cards, two HDs, one optical drive

2) Q6600 overclocked to 3.6ghz, two Radeon 4850 cards, two HDs, one optical drive

I think the 4850's draw about 100-105w at load but I'm pretty clueless about the CPUs.

Try this online PSU calculator:

http://extreme.outervision.com/psucalculatorlite.jsp

Seems to have enough options to look like it might be accurate-ish...

Thanks, that calculator's pretty useful although it doesn't appear to have the AM3 CPUs listed yet.

The recommended PSU rating defaults to 38w and adding just the Q6600 pushes it to 107w. If I set the overclock settings to 3.6ghz @ 1.5v, it calculates the CPU wattage as 205w, which pushes the recommended PSU rating to 186w.

Adding two crossfired 4850s pushes it to 368w and two sticks of DDR2, two SATA HDs and an optical drive sends it to 452w, so I guess I ought to be looking for a 500W PSU to be safe.