Try the Tacon 4074, it's cheap and has TONS of power. I use it on my Tekno V4 Ve8, and I love it. It's almost equal to a Castle 2200kv. Btw, the Tekno V4 Motor Mount that comes with the kit has a limit of 42mm, I believe.
http://www.hobbypartz.com/96m802-4074-2150kv.html