There is always a lot of debate about this point, but IMO the chassis (within reason) doesn't make a lot of difference in stock classes. Not nearly as much difference as the driver makes at least. In 17.5/27T stock a solid driver with a box-stock TA-05 (or TC3 or Cyclone S or whatever) will beat an inconsistent driver with a TC5 or 416, etc. For 13.5/19T you really would benefit from TRF shocks, front universal shafts, and a few other bits, but you'll still have fun without them if that's what you're after.

What chassis do you race in stock class?