What is your budget?
Are you going to be using it for gaming and where are you purchasing from? Also, do you need an os/monitor keyboard/mouse etc or just the desktop itself. Note that if you spend a bit less on a socket 1156 build you will have more money for a better GPU and the computer will be faster in gaming performance. Up to you though.
LGA 1366 supports both dual and triple channel, so it is not a problem if you get 4GB ram
Triple channel gives you small increase in performance
Yeah, but you may as well go with a 1156 socket + intel core i7 860. It will give you the same performance, but the motherboard will be cheaper.