Your processor and power supply won't bottleneck anything but your ram might.
The 660 Ti is good but obviously the 670 is better, honestly you wouldnt need anything better than a 660 Ti. I you bought one of those, you could get some more ram too.
It depends, what is your budget? A 670 would be great if you have the money.
Also consider not getting an EVGA card and try a Gigabyte, MSI, or ASUS.
Cheers for your comments, good to hear my systems still got some life in it, and i might also treat myself to some ram for Christmas. budget-wise anything goes i just didn't want to overkill on the graphics side, as I'm only using 1 screen at 1920 x 1200
Seeing as you're not limited on money and are only going up to 1200p, get a 660 Ti, there isn't that much difference between that and a 670 for the money.
Get the ASUS Direct CU II Top or the MSI Power Edition.
The MSI will be cheaper but the ASUS will be quieter and cooler with both having little to no performance difference. (Prices apply in England)