explorer
I have discovered that the Griffin is a hoovercraft - don't know what the proposize but lets guess 8 inch x 4 or 6
The ebay site your pointed to is heli - based, and all the motors I looked at are in the 4000 to 5000KV (Helis use BIG gears)
Say you ran only a 7.2 V pack this would give you 7x4000 rpm 28000 RPM at the prop which on an 8x4 is in the region of 2 KW (working from memory) and the tips would be well into the noisy sub-sonic region
These motors would be the canine pendular appendages if you were running a 4 inch prop, ducted fan impeller or waterjet, but I feel that someting in the KV1000 to 2000 range (aircraft) range would work more reasonably
I'm making lots of guesses, and relying on my memory a lot in this answer
andrew