The 645 is SLOW!!!!!!!!!!!!! Try a AE or Ace same thing just different stickers.
http://www.amainhobbies.com/product_...oducts_id/5733
This one is cheaper but not quite as much torque and if all you do is bash will be OK
http://www.amainhobbies.com/product_...oducts_id/5994
Or here is the same thing but with an AE label
http://www3.towerhobbies.com/cgi-bin...?&I=LXTCX8&P=0
http://www3.towerhobbies.com/cgi-bin...?&I=LXTCX9&P=0