As long as you are planning to learn to fly glow planes with a flight instructor, there's no reason you can't move up to a good low-wing trainer airframe like the Sig Four Star, the Goldberg Tiger, the Phoenix Models Dolphin, or the World Models Super Sports. If you've gotten a decent amount of stick time with your two GWS electrics, your biggest hurdles will involve simply learning how to tune, maintain, and operate glow plane systems.

If you won't be flying at a club with a flying instructor, then you're going to have your hands full just learning how to safely fuel, start, tune, and maintain your first glow aircraft. Adding a more challenging flying dimension should come later if this is the case.

Instructor = low wing trainer
no instructor = stick with a high wing trainer aircraft for a while

Good luck and good shopping!