This is a bit hard, because NVIDIA just released their GeForce GTX 650 Ti Boost GPU. This will force NVIDIA's partners into pushing out new GPUs in the coming weeks and months. This will also hopefully drive the price down of the GTX 660 and 660 Ti.
If you still wanted to buy a GTX 660 or 660 Ti, then out of those companies I would probably take a closer look at MSI's Geforce GTX 660 Ti Power Edition. It comes with a Core clock of 1019MHz, and 2GB of RAM and a very nice dual-fan cooler.
MSI make some great products, but I would really wait a couple of weeks and let the dust settle on the GTX 650 Ti Boost GPUs.