want to buy Lipos

[jnev]

Right now that is about 19.2 volts, and since you said that you wouldn't mind more power, I'd get two 3s 8000mAH packs (one on each side) and wire them in series. There is a new Hyperion charger also that is supposed to be very good, and also has a built in balancer which is a nice feature.
http://www.maxamps.com/Lipo-8000-111-Pack.htm
http://www.maxamps.com/EOS0610i.htm

Edit: As serum said, 6s would be pushing it a little, but I thought I'd mention it since you said you wouldn't mind more power. I only linked to Max Amps packs because the topic was originally in their section. But there are better lipo's available....