I have the Xray as well as 99% of the other micro racers around here , and love mine. But, last night a guy dropped a RS4 on the track in stock class and that thing was a rocket! It really got me thinking on whether to switch up. Now IMO, the Xray has no equal in the mod. class.
I agree with Shookie, check out
http://www.one18th.com/
They have a more rounded site covering all of the micros, not just the RS4.