I've used a hobbywing 1s and Orion R10 pro in my RB6 and both fit well, I think the reventons are a bit bigger than those two (maybe not much more than the 1s though) and depending on which cells you are running space may be an issue - The R10 fits very well, maybe look for a good 2nd hand one within your budget...
Also have run an HW V2.1 120a in my 4wd without a hitch, the HW stuff is rock solid and that is a neat size speedo, the V3 looks v nice
Never run a reventon and had no experience of them myself, but I've not heard the best reports of them, just sayin'...
