Hmm. Everyone at my club seems to recommend a lowing like the cherokee, goldberg tiger or sig 4 star as a next plane. The avistar elite is going to fly similar to you trainer in low rates, but much better aerobatics in high rates. A lowing airplane will probably be even more aerobatic capable. A cub will teach you taildragger takoffs, and probably rudder on turns.

Hard choice, but mine would be a sig 4 star. It's a low wing, and a tail dragger, teaching 2 new things, but at the same time probably not to hard to fly if setup correctly.

Hubert