So Q6600 G0 stepping, 2x2GB 6400 and say an 8800GTX...can my OCZ PowerStream OCZ520ADJSLI EPS12V 520W Power Supply handle it? It currently handles the X1800XT-PE/4400+ x2 just fine...
If it can deliver enough on the 12V lines, it should work. That will be the critical mark, since 520 watts is more than enough for that combination, even for the non-G0 steppings. For comparison purposes (reposted from here):
Taken from X-bit Labs' 1000 Watt PSU review:
Intel-based system:
* Quad-core Core 2 Extreme QX6700 CPU (Kentsfield) overclocked to 3.5GHz
* Two Foxconn GeForce 8800GTX graphics cards in SLI mode
* ASUS Striker Extreme mainboard (LGA775, NVIDIA nForce 680i SLI)
* 2GB DDR2-800 SDRAM (Mushkin XP2-6400PRO, 4 x 512MB)
* Two Western Digital WD1500AHFD hard disk drives in a RAID0
* Various trifles like a DVD-ROM, fans, etc