which one?

The one you recomended on the first page of this tread.

setup # 1
6s lipo 5000mah
1600kv motor
+ charger

Setup # 2
pq4s 3100's in paralell
2400xl
+ charger

Nice truck :D

I have a pair of Polyquest 4s 3100mah packs, that together weigh around the same as 8-9 cells. These, wired in parallel and using a mild motor like the Lehner basic xl2800 on a light truck (9 pounds +/-) would perform very well(fast enough to spank the Novak system) and have a nice, long runtime).
The 5000mah 6s pack is not something I have, but merely a suggestion that would provide excellent speed, power and runtime. For extended runtime, cooling measure are a necessity for most systems.

Can you give me a estimated cost ?. I'm just wondering.