I mean, Amazon sometimes has them on sale plus giving an Amazon gift card on top of that.
You don't need anything more than the most basic 4GB, no-hard-drive Slim. Yes to HDMI and composite. You don't need a controller; all you need is a simple Media Center remote control. There's an XBox Universal Media Remote that works great; get the older white one, not the newer black one.
Mine are strictly extenders. They boot into MC, and that's that. With the remote, I can easily also use the DVD player. It's nice to have that.