You could use the Tacon 25 offered by Hobbypartz. I use the Tacon 46 in my Great Planes Extra 300 and it has more than enough power, reliable and is very reasonable.
http://www.hobbypartz.com/96m603-big...826-870kv.html
I love the Wunder, had one years ago with an O.S. 15, it was a BULLET!
Good luck!