heres a Traxxas esc with reverse, $39. Handles 17t and 7 cells. You should add a small cooling fan.
http://www3.towerhobbies.com/cgi-bin...?&I=LXJM28&P=7
heres one i use in alot of my rc's, $34. Handles 12t and up and up to 10 cells. Forward only, but great bang for the buck.
http://www3.towerhobbies.com/cgi-bin...?&I=LXD523&P=7