Brian,

That info does help. First things first--I think it will be in your best interest to lose the geared 280 in favor of a geared 300 type. 280's are an okay sort of motor, but you could achieve much more power from a 300 motor on 5:1 gearing with a modest increase in current requirement(the 10 amps speed control you have shoudl be fine). I spent a year fussing around with 280 size motors as an intermediate upgrade from IPS class( the tiny 150 size motors like what's in the GWS Tiger Moth) only to conclude that I couldn't find any real advantage over the original setup. If you bump up to a 300 motor, you will likely be looking at current in the range of 6-8 amps instead of the 3-4 amps the 280 is pulling, but the actual output power will be improved. I'm assume(tell me if I'm wrong) that the gear box you are currently using has an open frame with 3 or 4 mounting ears which bolt to the firewall? If so, this is the stock wattage gearbox, which is excellent at making gear noise but horrible at making an electric motor spin a propellor. I would suggest you replace it with an EPS350C motor and gearbox combination from GWS(fabrication of a stick mount will be required). This will get you a "350" motor--a 300 timed for reverse rotation, and a dual ball bearing gearbox in your choice of ratio for ~$15. 5.33:1(GWS refers to this ratio box as "C" gearing) is the most popular, and work well with 7-cell nimh pack or 2S lithium polymer on a 9x7 GWS "RS" prop.
Now the good news, if you haven't figured it out already: the battery you have should be fine. 2/3AA nimh packs are usually capable of sustained current draw in the range of 6-10 amps, so you don't have to buy a new battery.