I guess I stand alone on my vote for OS for cheap ARFs. The Evo engines like 4 stroke plugs, what do they cost nowadays? My SF and FSR OS engines haven't let me down with any liner issues being careful not to abuse them running them lean, or have I ever suffered power issues in 20 years of flying, but I turn over most engines after a few seasons than face the rebuild price. The FX I understand takes chrome liners from ASP, and not subject yourself to a crappy carb, which is what I want most, is tuning quality.
If I want "more power" I'd get a Rossi. For sport plane flying, the OS carb has the best tuning, transition of any carb I've tuned. My OS engines were made in Japan. Have no intentions of ever buying a "new" engine. Not with so many giving up glow, you can pick one up for $30-$50. For chrome, I've enjoyed the Thunder Tiger Pro, and yes, it has sport plane power. Abandon the thinking Evo, Magnum, ASP, OS, Thunder Tiger, Enya, are going to cary more than 500-800 rpm, they're not going to. Throw a 9X6 prop on a Rossi .40-.45 and get .60 like fuel consumption at 16,500 rpm and blow your ailerons clean off your ARF. The idea of trainers and low wing trainers, isn't an extra 10 mph speed, but to develop good flying skills, enjoy landings, and mild aerobatics. Jett or Rossi on the right pylon / pattern / quickie 500 plane will give you all the cheap thrills of performance, and durability of higher quality, that comes at a premium price.