Basically you could do that indeed, however, as you mentioned you HAVE to make sure your PSU is good enough.
Furthermore you also have to ensure that you have enough physical space in your case, the 6950 is a HUGE card, so take some measurements making sure that it fits.
As for your CPU, it's ok, defenitely not the best out there, but should be good enough. Might want to consider a step down in graphics card with that CPU though, a 6850 should be more than plenty powerful, and more likely to physically fit.
I was severley cramped, 2 sata plugs were in the way but thankfully they were surplus to requirements anyway.. a built on external HDD hub thing and memory card readers that I never use anyway. Unplugged them and everything seems to be ok for space. My motherboard obviously wasnt expecting any monster graphics cards.
next step.. MOTHERBOARD! lol.. id better up my overdraft limit. next year perhaps.
Not a bad spec pc, but just can't deal with SWTOR too well. WOW was quite reasonable on it, had settings quite high.
ah, forget the overdraft limit thing, i was just on about how a new interest in upgrading's going to cost me.
in my PC i have a small unit at the front with adapters on it for memory cards and similar. i never use it, but it's connected via a sata cable on the motherboard, there's a diagram of a few of the sockets on it, eSATA, MS/SD/MMC, CF, SM/XD. Ive never used any of them so I doubt I will start to.
The space I have should just about be ok, ive measured up and with the 2 sata cables unplugged the space available appears to have been sorted. I still have my CD and HDD hooked up so it's all cool.