Losi makes a strong car I have not had any problems with mine, I have a 8ight pro but I race with someone that has an RTR with the stamped towers and he fliped over, not a bad flip but it bent the crap out of his towers. The stamped towers and chassis are week I think so I would replace them. Even being a little out of strate will change the cars handeling. As for he KHz vs the losi its all a matter of do you want black towers or the towers from losi, they are the same just paying for the KHz name or you could go with carbon fiber to shave some weight.
For the servo I havea JR 9100s and its awsome but it does cost a few dollers. But i have a HS 945 (replaces by the HS_985mg) in my SC8 and it is more then enough speed and it does not cost as much as the 9100s or the XP-1313. But it all depends on how much you can spend
http://www3.towerhobbies.com/cgi-bin...&I=LXMUS4&P=ML