Look at a Himaxx brushless from http://www.allerc.com these are probably the most reasonible priced brushless motors.
You might try a http://www.hobbypeople.net/gallery/131480.asp cobalt motor, the price is great, you can probably use you existing
speed control and battery and this will be a big upgrade over stock! Use a 6x4 E prop instead of the usual 5x5. I have an EdgeRC Overlord wing and nobody with a Speed 400 can keep up.
The least expensive brushless combo would be a Himaxx with a Phoenix brushless controller about $130.
You must use a brushless esc with a brushless motor!!

Good Luck