The most for the least is going to be the Tracker II by Polk's Hobbies.
For $275, you get a programmable 8 channel radio which has synth built in (ability to choose any of the ground freq's you want). With it at that price also comes a synth receiver including 900mah batteries for both the TX and RX, but you'll have to shop for your servos because it comes with just one.
But for a boat, you can get the cheapest servos out there and save a bunch of money that way.
Make sure that you ask for the ground frequency (75mhz) version whatever brand of radio you get.
The Tracker II offers 3 mixes of any of the 8 channels, so if you buy two radios and mount them side by side on a tray, you will have the ability to select which frequency either of the radios work on as well as to mix whatever channels you might want to make things toot and putt on your boat.
So, 2 (two) synthesized Transmitters AND 2 (two) synthesized Receivers that, together, will do everything you want and for only $550.
It will be hard to get that much for that little.
http://www.polkshobby.com/
Highflight