Also consider a 2s lipo pack.
I purchased a Great Planes 2s 1500 8C pack over a year ago for my Mini-T. It works fine with the stock electronics. You just want to watch for when it starts to slow down, or better yet, get a low-voltage cutoff device.
Here's a link to the pack I got:
http://www2.towerhobbies.com/cgi-bin...&I=LXGHE5&P=ML . Of course, this means you need a lipo charger, but if that's all you're using it for, you can get away with a $30ish 2-3 cell lipo charger. Heck, there's even a 1A wall charger for 2s packs for less than $10
http://www2.towerhobbies.com/cgi-bin...?&I=LXLGP8&P=7 .
My 2s pack also works great with the Mamba 6800 system, which lets you know it'll handle an upgrade to the electronics as well.