I use Tower Hobby, but I've recently ordered some servos from a Chinese site. I will be testing them and seeing how easy (or not) they are to waterproof. But for your purposes, plain old Futaba S3003 standard servoes are fine at $9 each. Do you know what kind of radio system you're going to buy?
I would guess what u said the 6 channal 2.4 GHZ. but opinions on the better manufacuter and if an extra channal would be of any use.
I'm using a Spektrum DX-6 that I got from BC. Works great, although I replaced the battery in the transmitter(notoriously short life on it) and soldered in a new voltage regulator, which was probably overkill. Most people just swap in a new battery. Initially, you can run around on the stock one.
