<200 I would get the g&g combat machines... their gearbox is very friendly to techwork but a bit on the fragile side... the KA gearbox is stronger, but a pain in the ass if you want to put in faster gears. The KA externals are nicer than the CM line though.
The next price to even consider would be vfc at the high end. Most compatible, highest quality externally, strong gearbox that's easy to work in that takes mods very easily... without dremelling to make room etc, unless you want to put a mosfet INSIDE the gearbox, but that isn't even an option with KA.
I futz with V2s, V3s and V6s. I could be wrong... but probably, most likely not, as far as I know.