These Sandy Bridge cpu's run cool. You could get by on a more inexpensive cpu cooler like this one down below. Also if you plan on over clocking and running dual 570's in the future I would consider an 800+ watt psu.
I think you can go even cheaper on the cpu cooling. Like Why_Me said, the sandy bridge chips run very cool. I think spending $35-$45 (USD) on a decent air cooler is more than enough. I would recommend either the Coolermaster Hyper 212 Plus or the Scythe Mugen 2 Rev B. I have the scythe, and it is very efficient at keeping my i5-760 at very low temps.
I also agree that if you want another easy way to save money, get the 2500k. But as webdev pointed out, the 2600k will be superior if you will be doing a lot of video encoding.
That motherboard is nice, but if you thought you would never go SLI, then you could get something cheaper.
The only other thing you might do is instead of getting one 128 GB SSD, get two smaller SSD's and put them in a RAID0 array for better performance. I would check to see if you can find any deals that would make the 2 SSD's cheaper than the 1.
SSD - The Vertex 3 stands alone at 550 MB/s read and 500 MB/s write
CPU - Since it's a workstation and a gaming rig, the 2600k makes prfect sense. With 8 threads, it will run hotter than the 2500k. I suggest using a MoBo that allows you to save BIOS profiles. I'd set one up at 4.4 Ghz for 24/7/355 "everyday use" and another at 4.8 Ghz w/ HT turned off for gaming use.
RAM - If ya workstation is going to benefit from the 2600k tho, it will also benefit from lower latency RAM. I'd look for a CAS 7 set like the Mushkin 996981 .... it has no pointie things to hit CPU cooler
GFX - I'd look at twin 560 Ti (900MHz version) .... 570 gets 524 fps in Guru 3D's game test suite to the 560 Ti (900MHz)'s 495 but it's only bout 2/3 the cost. In SLI, the 560 (900MHz) gets 862 fps to the 570's 873 .... again for 2/3 the cost. Don't kno if that ratio holds down under tho.
Cooler - Since it will function as a workstation, gotta imagine you don't wanna hear whirring fans while working. In the UD4 or Asus P9P67 Pro, the Kuhler 620 would solve that problem. It's very quiet and outperforms the Corsair H50 considerably. Similarly, the Kuhler 920 outperforms the Corsair H70 but they quite a bit noisier. None of them will fit however if you upgrade your MoBo as recommended below.
For air coolers, again, noise is a big issue w/ the Coolermaster V6 GT The big dog in the room is the Thermalright Silver Arrow which is extremely quiet w/ its low rpm fans and BMR calls the "ultimate air cooler" but as they also said, it's overkill for Sandy Bridge.
I think the Silver Arrow represents the ultimate air cooler than can be built and still fit within the constraints of an ATX motherboard and a standard computer case. ..... It's almost ironic that coolers like this are becoming available just as processors transition to designs that may ultimately render them unnecessary; even overclocked to 5GHz, an Intel Sandy Bridge 2600K doesn't need anywhere near this level of cooling. Still, it wouldn't hurt, and as I noted earlier, there are still CPUs out there that can benefit from it.
You can grab a Scyther Mugen 3 (SCMG 2100) ... It's outperformed the venerable Megahalems on some tests and costs half as much at about $40. Here's some recent reviews ... you'll note the Noctua has fallen to 2nd tier status in the 1st one.
PSU - The HX750 is a great PSU, but you'll want the HX850 if you thinking of adding a 2nd 570 in the future. Up top here in the US, the XFX Black Editions offer equal quality and performance to the HX but much less hurt on the wallet with the XFX Black Edition Models.
Case - No front USB port concerns me .... consider the HAF-X or DF-85. The DF-85 isa $10 cheaper on pccasegear.com and can be paired with the CP-850 to save $55 over the Armor + ($190) / HX750 ($195) combo .... and no more concerns about the 2nd 570 being added down the road.
MoBo - Finally you have to decide whether the x8 x8 limitations of Intel SB chip is a concern for you. This limitation is overcome w/ the addition of an NF200 chip. I take it seriously when GFX card investment is in the $400 range with a 2nd card in SLI or CF eithe rin original build or planned future upgrade. Again, if you are sure you are going to use only one card ever then no need to concern yaself w/ it. But looks like you were aiming to size your PSU for two and you selected a CF / SLI MoBo. Read this article to see the impact: