Just so you know, display took a bit of configuration for it to work with hdmi. Can easily be used with composite but you are limited in resolution then. The best place to get one is ebay. You may pay a couple extra bucks but at least you will get it fairly quickly. Mouser electronics has them too. Getting one from the main raspberry pi site will take you 3-6 months to get. They are that far in back orders. It does not include a power supply. It runs off a usb power (5 volts) or a case.

I dont think it is real powerful and if you are looking for horsepower in a small size, I would say to go with micro-itx or mini-itx.

They also have minecraft and mame for raspberry pi. I haven't tried either yet.