You won't see much improvement with an upgrade to GTX 660, 660Ti or 580. To get a good upgrade from GTX 570, you need a GTX 680 or 770.
Consult Tom's Hardware's Best Graphics Card for the Money graphics card hierarchy chart:
http://www.tomshardware.com/reviews/gaming-graphics-card-review,3107-7.html
In order to get appreciably better performace, you need to upgrade at least 3 tiers up. Your suggested upgrades only go 1 tier up.
I would suggest you hold tight and do with your current GPU. Next year both AMD and Nvidia have genuinely new GPUs coming out on the new 20 nm process. Those could be much faster than the current models.