I'm sure you have all seen the question before "GTX 560Ti vs 570 vs 7850..." Well I'm going to ask it again! However there are a few things I want to get out the the way first...
1) I don't really plan on over clocking unless I see fit.
2) I will probably upgrade in a few years.
3) My monitor is an ASUS Asus VE276Q 27".
4) Not too important but a black one would be nice...
5) I have a 650W PSU with i5, Kingston 8GB, 1 SSD, 2 HDD, optical drive and fans etc...
6) Willing to upgrade PSU but hope not to.
7) I have a 600t so can house pretty big cards.
One last thing, say I was to SLI the GTX570 MSI TwinFrozrIII would my PSU handle it with enough juice left to power a new i7 2700k?
Depends on the exact model of your PSU, but I'd say no. I wouldn't recommend it, even if the PSU could actually do it, as you would likely be pushing the PSU to 100%+ of its rated power draw, which isn't a great idea for long term use.
Seeing how I run an i5 1155 I think that the card would cause allot of bottle-necking.
There is no i5 1155 that will be a bottleneck for any single graphics card made in gaming benchmarks.
i7 3820, i7 2700K, i5 2500K, i5 3570K, and the i5 2300 will all show similiar gaming benchmarks with a GTX 670. You'll see maybe 3-5 fps difference between them.