IMO you're cutting it close with 36A 12V, SLI 8800GTS, and such a power hungry CPU. I definitely would avoid overclocking it.
Running prime 95 + 3dmark vantage at the same time, the OC'ed X4 9950 (edit: total SYSTEM) consumed nearly 640W at the AC source with an HD4870x2. Had we been using Furmark rather than 3DM, it would have been much higher. http://www.tomshardware.com/reviews/amd-cpu-overclock,2304-13.html
Stock you may be fine, overclocked likely you'll have issues. Either way, if the PSU can't provide peek demands, you'll suffer stability issues.
Not a close enough comparison, but for 1.5+ years I've run a 3.0-3.2GHz Q6600, Dual OC'ed 8800GT, 2 HDD, 2 opticals with an Antec TP3 550W and 41A 12V.