Both of those CPU's should be fine to pair with either card. TechPowerUp does a lot of comparisions at different resolutions to consider. During their review of the reference model 650 Ti Boost 2GB they compared the relative performance of the card against many others at 1280x800 resolution, close to 1366X768:
Compared at stock speeds on reference cards you should get somewhere in the neighborhood of a 9% performance increase.
When you say maxed out it do you mean with everything turned on and up to the highest settings? Both cards may not acheive that standard; however, either the GTX 650 Ti boost 2GB or the GTX 660 should be able to handle enabling the intensive settings and look fantastic at that resolution. I would opt for the 2GB 650 Ti Boost still over the 1GB for better performance for about $20 more.