Before you spend any serious money I would suggest you visit BAT or SCAT websites and take a look. I don't know when their next event is but I would suggest going as a spectator. Shooting BB's is nice but having to work team mates to outsmart your opponent is very cool and the best tank for those kind of fights is the Tamiya line of Full Option tanks. For less money the VS-Pro line with IR are good.
http://www.bayareatankers.org/
http://web.mac.com/ksoc/iWeb/S.C.A.T./Welcome.html
I am suggesting them because if your in CA they would be closer then coming over to AAF in Danville VA.
You're of course welcome to visit
www.heatarmor.com as well
Regards,
James