That is the setup I have, minus the ti. Most games will run on ultra at 30fps or a little better at 1080p. But going forward, 2015 will probably be the year that the 660 and 660ti will have have to start playing on high settings and in 2016 medium settings will be what they are capable of. That is just a prediction based on my experience of playing games for the last couple of years on my pc. That said...in 2016, medium settings will look like today's ultra settings look, so games won't look bad.
Since the i53570k will still be great for gaming for several years to come, I'd say go ahead and build that system since you already have the MB and gpu. You can always upgrade the GPU by itself when it can no longer do what you want. But for now it is fine unless you absolutely insist on have 60+ fps at max settings on every game that will be coming out in 2015.