[JThiessen]

Well, the Neu 1515 1Y seems to be the general consensus for the revo. I run a 1515 2.5D, but it kinda forces me into 5S or 6S batteries. The 1Y runs well on 4S.
Others will have to provide input on the Medusa. I seem to remember someone saying the 70 series would be a prefect fit, and also that there are 80 series coming in about a month. Do a search in the brushless forum for Medusa, and I'm sure you will find plenty to read.

For motors, you kinda want to stay in the 2200-2800KV range for 4S batteries.

Also, dont forget gears. Since you are using the stock revo tranny, you will need some 5mm Mod1 pinions.

Check out the speed calculator in the brushless forum. Play with it for a while with different combos for a little while. I can be a little confusing at first, but you will soon get the hang of it. Keep an eye on the motor RPM when you are trying different combo's - you'll want a set up that keeps the rpm's over 30K at top speed. Gear it for 40-45. The motor selector calculator will also help you figure out the different motors.