Well ya get what ya pay for....mostly. I started out with the exact same combo (hs55s and hs81). Eventually I stripped gears in the 55s and went to hs65s w/ karbonite gears all around. They're not indestructable but they are pretty stout. Now however, I'm using JRs (JRPF300H) Performance Mini Heli ServoSet (159.00 @ heliproz.com) These servos and the carbon fiber frame kit (also heliproz.com 58.00) were the 2 most significant upgrades I've done on the rex, and beleive me I've done them all (though i like futaba's s9650 better than the JR for the tail). I've used every servo mentioned in this thread and more. As far as the CF frame goes if you've already got an SE or SA you're already set, it's just the plastic frame with all the sloppy linkages that sucked.[:'(] Anyhow that combo will get you some airtime, just make sure not to overdrive any of those servos.
Hey Kurtzz it so happens I need an s9254 for my caliber 30 and I have a s9650 that has never been touched by human hands. You show me yours and I'll show you mine.