Out of those three GPUs, the MSI GeForce GTX 650 Ti Power Edition is definitely the way to go. If we were comparing the GTX 550 against the HD 7770 - then I would've suggested the HD 7770. But the Power Edition GPU from MSI is pretty damn good.
Because of your low resolution (1366x768) you'll find most GPUs will be bottlenecked, so any GPU in this price range should perform quite well. The MSI GTX 650 Ti Power Edition actually overclocks quite well, and performs at higher resolutions admirably.