The rtr servos and radio are pretty good for a rtr i havn't felt the need to replace the servos but i may go 2.4ghz just to max my time at the track. The newer rtr comes with the the much better sh 28 engine as well. Stock rtr tires are pretty good if a little soft and can balloon easily but pretty good considdering. The best upgrade other than what you have already said would be the springs, get the mugen red springs, got mine for $12 delivered, they are longer and have more coils and can even be used without spacers.