If you are talking about 46 size sport engines then there is not all that much difference in power from one to the next. I agree with Ed that the OS 46AX is a great all-around engine. I run a pair of these with Ultrathrust mufflers on my Twin-Air.

Rossi's and Jett's are a different class of engine. I never owned a Rossi but I put a pair of Jett 50's and tuned pipes on my Duellist that I just maidened today. Ground peak with 9.5x7 props is right at 18,000 RPM and they are still breaking in. These engines are designed to run smaller props at extremely high speeds and make a lot more HP than the sport class engines.

Walt