I run the new medusa 50mm 4800kv and HIGHLY recommend!! It's prefect on 2s doesn't stress at all and is perfect in these 1/12 truggies....
PS a 2s 5000 will run as long as a 3s 3400mAH and it won't be any more effecient, these little trucks even racing don't push it hard enough. If you were going 4s, now that would make a difference, but then you would need some really low kv motor to hold up. Keep in mind you should be able to fit a 2s 6000-8000 pack if you wanted and since a 3s packs is larger in size and weight you can go w/ a bigger pack sticking w/ 2s and like you said a sidwinder esc is pretty attractive.
http://www.youtube.com/watch?v=xCJlp...e=channel_page