Don't think you have to stick with OS or top engines either. The tower engines are good, TT engines are good, super tigre engines are great. The FX does have more power than the LA series. You can look at the power charts to compare engines on towers site. Look at the tower engines too. For the money, you might be well ahead to look at those.

Most of the engines are good. You just have to find one that will work for you and work for more than just the plane you currently have.