I have almost the exact same setup except I'm running two XFX GTX260 Black Editions in SLI, and have an Asus P6T mobo. It runs Crysis Warhead on my 24" widescreen @ 1920x1200 with the settings at max (8x AA).
The 750TX runs my system just fine, as far as I can tell. With only one card you will definitely be set... I don't know too much about the ATI offerings, but you can check out the comparison between single and multi-gpu performance here: http://www.anandtech.com/video/showdoc.aspx?i=3517
You don't need an aftermarket CPU cooler. Leave that to overclockers.
@Maverick_i7: your 750TX can support two GTX 260 cards, yes, but you're pushing it outside its optimal range. I guess you'll be fine with it unless you overclock the CPU and add a bunch of hard drives and a TV tuner and so on. nVidia's recommendations for GTX 260 SLI are here, btw: http://www.slizone.com/object/slizone_build_psu.html
You do not have to buy into the hype that an ultra-large PSU is necessary for SLI/CF. Even in Anandtech's recent multi-gpu reviews (2-way, 3-way, and 4-way) the maximum 2-gpu setup's total system loaded power was less than 500W. This was with 2 285's in SLI. Both Anandtech and TH have made comments on industry pushing unnecessarily large PSU's on consumers. Just make sure your model has the required connections and amps per 12V rail for your rig.
The brand / model I personally use for my i7/SLI'ed 260 c216 setup is the Silverstone ST70F 700W SLI/CrossFire Ready 80 PLUS Certified modular PSU.
Per Anandtech's recent System Buyer's Guide:
"The Silverstone 700W has made almost everyone's top performance list for a PSU and it is a good buy at its regular selling price. At the current selling price of $100, it is an outstanding value. The Silverstone is a modular power supply with the flexibility offered by custom cable selection and arrangement."
The ST70F also won TH Best of 2008 award.
Both the PC&Cooling and Corsair models are good choices too. I chose the Silverstone over the Corsair because I wanted a modular PSU and didn't want the 12 other non-used cables taking up space in my CM-690 case. Some modular designs use subpar connections designs; however, SS's is rock solid.
You can also look at a PSU's power efficiency at this site or others to check how your particular PSU's efficiency varies as it is stressed.
I have seen a lot of posts saying that even non overclocked i7s should have an upgraded CPU cooler as the stock one is just not good at all. I don't know from experience though. Also, IMO, I would upgrade to a little on the power supply, the 1200 case has 6 120mm fans and a 200mm fan on top, thats a lot of power just for the fans, along with a large GPU, fast RAM, large HD and an optical drive, for the few extra dollars, I would go with a 1000 watt just to be safe, better to have too much power than not enough :-)
the 1200 case has 6 120mm fans and a 200mm fan on top, thats a lot of power just for the fans ...[/quotemsg]
Another uninformed post, typical case fan power draw (even its max stalled power if the blades are obstructed) is typically in the 2, 3, 4, 5 watt range. That is not a lot of power at all and continues to misinform people on power requirements.