Wow you've really done your homework! Nice build there.
GTX 560Ti is a solid card, it will run all current games maxed out (aside from maybe Metro 2033) with a good fps (30+). The 750w PSU you've listed would be enough to run your build with 560Ti in SLI. Buying a single card now, and adding a second in the future would be a nice upgrade path, great performance, without breaking the bank.
GTX 580 - Single card will obviously run everything released so far maxed out with good FPS, and should be fine as a single card for a good period of time. Of course that then allows you to add another 580 in the future if you ever needed to performance boost. SLI 580's are recommended a 1000w PSU.
Generally its my view that you should never buy SLI cards right off the bat, buying the single most powerful card you can fit into budget, allows for good performance, and best upgrade options in the future.
GTX 570 is a good "mid-point" (also consider ATI 6970), but doesn't perform much higher than overclocked 560Ti's.
Bottom line really comes down to how much you want to spend, and what performance you wish to achieve. Rumours suggest a GTX580 is needed to max out BF3 meaning choosing a single 560Ti now, could potentially require you to add a second card if you wish to max BF3. Obviously though, this is rumour, not fact and since the game isn't released, we wont really know.
Budget Air cooling: Hyper 212+
Best Air Cooling Option: Noctua NH-DH-14
Closed water loop: Corsair H60/H70/H80/H100.
As far as i know the Noctua will perform up to and higher than the Corsair H70. Im not sure however how it compares to H80/100.
IMO the WD 1TB FALS is not really a good choice for a 1TB harddrive. Firstly there is the Samsung Spinpoint F3 1TB which is cheaper, faster, quieter & cooler than it. Then there is the the WD 1TB FAEX, which again is beaten by the Samsung, but it will at least outperform the FALS.
One of the criticisms of PC-90 is that the HDDs are mounted on the left side panel, which can mean that it can potentially be a PITA to get into the system to do any maintenance. So also long as you don't mind this hassle, or don't go into your system very frequently then it's a good choice.