I run a Mugen .12 in my NTC3 and it is a bat out of hell. I purchased the 2 speed kit, 4wd, rear exhaust and bump start kit. Its wonderful.
You will find a lot of good choices out there!
Some are VERY expensive while others are VERY cheap. I would almost always recommend staying away from the cheapest ones around. In this hobby you will get what you pay for. Dont get me wrong, there are some really nice inexpensive kits I would get and run without fail. Just stay away from the really 'cheap' stuff if you can. You will be happier in the long run and less frustrated.
What price range are you looking for?