real simple, first what parts do you need, generally as a rule you will buy the SRX parts. they will be the best upgrades, but first to tell what you have is look at the canopy, is it more rounded or pointy. the dx had no bearings all bushings and metal flybar paddles ( but most change the paddles so even a dx may not still have them) the SR-t / SE / SX / SRX have the pointed canopy, the SR-t has a longer main shaft and no autorotation bearing. the SE SX SRX has all bearings and metal balls, the SRX SR-T has new style grips the others have the old 2 piece blade grips. the SRX has a different rigid servo frame which is vertical for 3 servo's the dx style has 3 servos facing up and is quit flimsy. the SRX parts are all a direct fit on any of them except the blade grips you will need some bearings and other parts, so generally if you need something get the SRX, also the SRX had a 2mm tail drive wire, which is a must for any concept flyer, the 1mm will break many times, but you need the wire and the tail coupling to use it.

hope it helps

JOn