if you are just bashing then i would defently suggest 4 cell, since a 4 cell car is much cheaper (you can buy 2 6-cell packs and then make 3 4-cells) also the tire wear is less (since an extra 2 cells is alot of wieght in such a light car), and also your motor is less stressed, and its easier to drive.
12th scales dont break that much (even running mod). the most common things to happen are chunking tires and cracking bodies, but its VERY rare that anything on the chassis will actually break (its not like a sedan or offroad car where you can break an arm or hub or something like that). also the speedmerchant car is currently sold with the old style AE front end (until the V-force comes out), and you can put the AE dynamic strut on (which is better for asphault than the old style one) without modifactions, and that is the only real chassis peice that you can break (Although it takes a REALLY good hit to break an arm, more likely you will colapse springs or ruin them in some way, and those are standard AE springs). the rear pod on the speedmerchant is the same as the AE car, the main difference is in the battery location and how it pivots on the rear end (which is actually alot more durable since you cant break t-bars like on the AE car), and its almost phyically impossible to break (unless you hit it with a hammer). so the only things you could break are really standardized 12th scale parts, and there are less things to break on the rev. 3 than the other cars. also
www.hobbyetc.com sells parts for the car at very cheap prices.