A good friend of mine used to run his
mbx5t with 6s2p A123, Neu 1515/1Y (2200kv) + MGM 16018. Too much power for a track due to the high revving motor (around 40000rpm) and it could not be geared properly with the stock MBX5T gearing resulting in relatively high temps for motor and ESC.
As you consider to run 6s2p A123 in a truggy i would recommend a motor with 1700-1800kv (2200kv was too much). This way you will not run out of gearing options and you can always use a bigger pinion if you want your truggy to go faster. The MGM 16018 (now MGM 16025) or MMM ESC would be a good choice for 6s2p A123 in a truggy.
The 2200kv motor would be better suited for a truggy with 5s2p A123. I now run my Mantis truggy with 9s1p A123 (9 A123 cells) and it is still plenty of power and it gives 8 minutes of runtime on a track.
The beauty of A123 cells is their ability to be recharged in 15 minutes with the proper charging equipment. If you have a power source at your track you could run your truggy "forever" with only 2 battery packs. With 10-12 cells in your truggy, proper gearing and the right driving style you should be able to run your truggy for 10-15 minutes.