you can get the metal disk brake kit from cen for under $5. you may want to look into the dynamite mach .26. it has the mounting dimensions of a .21 but much more power. it goes for about $140 w/PS.

and about the radio, smart decision.

and it wouldnt hurt to upgrade the steering servo to one with metal gears. i have the futaba S3305 metal gear servo. it costs $35 at tower hobbies.