I think you`ve covered it well Bry, I`ve used both these type of motors and they cover my needs admirably. The 777s are the very popular up here for 48 and 72nd scale ships.
For smaller ships, Model Motors Direct do something called a Mecca Motor, I`ve installed these in My River class Minesweeper and they are brilliant little motors, I`ll certainly be buying more of them.
Graupner do a fantastic range of motors too, the speed 500, 600 and 700 motors would suit most warships dependant on size.
I would challange you about double the voltage double the revs though mate, you can easily burn out a motor by overpowering it, it always pays to check the designed voltage for the motor you intend to use
You must remember though, scale speed is controlled by the digits on your hand, the farther forward you push that stick, the faster the model goes, it really is that simple..... I must admit though, it`s sometime hard NOT to rush about the pond like a boy racer
If you use a computerised R/C set, you can alway programme it for each of your models, most modern speed controllers are very easilly programmed also