Another 'Enough Power' Question

[fellows]

Hey guys.

I just spent about 3 hours shifting power supplies from computers I had lying around to free up an Antec TruePower 550Watt PSU. I am hoping to use it in my next rig, as cash is problem at the moment.

-QX6850 [w/ Scythe Ninja REV.B + 120mm fan on the bottom] [getting it for $250 so please dont say 'forget QX6850 and get a Q660']
-eVga 750i FTW
-3/4 HD's
-8800gt
-The other case fan that comes in the Antec P182
-Audigy 2 ZS

I'm a little concerned about the QX6850, as most previous threads allude to 550W being enough to run Q6600's no problem. I'm wondering if I can do any OC'ing at all. Also since it is a SLI mobo... would running 2x 8800gt or gts' be a problem with this PSU?

On a Side note: I am currently powering my signature rig with a 430Watt Tisonic Power Supply. Unfortunately the PSU only has a 20-pin connector whereas the mobo has 24pins. Is this going to be a problem?

http://www.hardforum.com/showthread.php?t=1305233

That seems to go with what I thought, but some of my components are higher end (8800gt, 3--HDD's]