what is a good sized engine for...
Because of the balance issue with the Sukhoi, I'd wait for the next H9 33% ARF to come out. Or look around for the H9 Cap. The goal should be to get the plane down in the 24 lb range so you have more engine choices. I'd avoid the GT-80, not enough power/$. The least expensive option is the ZDZ-80. Any decent twin with power will cost $1200+ with mufflers new.
Don't know about the AW Extra. The 33% Edge is a good plane, but typically weighs 29+ lbs - so it usually needs a strong 100cc twin for 3D. You could wait on the Extra to find out how heavy they turn out.