I'm really not sure. I think the servo market is moving toward more HV servo offerings, servos that can accept 8.4v input. I've been shopping around for a BEC to use on my gaui 550. Castle creations has a 10amp nominal/20amp max BEC and the others I've considered are from Gryphon:
This one might be overkill for my setup.
This one seems better suited with 7a nominal and 15a max:
Personally I would use your sportBEC on anything up to a 500 sized heli (425mm blades) with no worries. Its been flawless on my stretched 400 with 350mm blades and is cool to the touch after a flight.
Of course the big trend these days is flybarless 3 axis gyros and the higher current demands placed on servos vs a flybar setup. I wouldnt know since I have only flybar setups.
I usually hang out at helifreak.com. I think I'll ask about servo amp draw over there.