thom7215,

Assuming all of the guts from the RTF Superstar are ok (radio, engine etc), then I'd be temped to get an ARF Avistar and plonk it all in. The Avistar will be a bit more of a challenge and it's always good to have a trusty ol' trainer to fall back on. Ask around, you'll find a lot of people keep a trainer on stand by for when they want to slow the pace down a bit.

As for other stuff.....

I can see where the progression from high wing to low wing comes in, a high wing plane has 'positive roll stability' meaning that the CG is under the wing and will naturally pull the plane back upright. A low wing plane may have 'negative roll stability' meaning that the CG is above the wing.
I have a Hobbico Brightstar (now discontinued) which is supposed to be a low wing trainer (looks a bit like a Cherokee), it has a flat bottom wing, a fair amount of dihdral, a trike gear and flies as slow as an average trainer. It does however, fly differently from a trainer. You can tell it has the negative roll stability by the way it falls into turns and wants to increase the roll, you have to be careful to maintain altitude, you also need to keep a little power on landing unlike the trainer which tends to float. Unfortunately, due to the wing, it is no more aerobatic then my LT-40 although it handles wind better.

Taildraggers can vary wildy in their handling. I was unfortunate enough to buy Sturdy Birdy at one point in my efforts to learn to fly. This thing (a taildragger) was a bear on the ground even a very experienced instructor had a lot of trouble getting it to track straight for take offs. I eventually got the hang of it and flew it for a while...

I actually went straight from an LT-40 to a H9 Funtana, I found the Funtana easy to fly around (using very low rates) and easy to take off. Landings required a bit of getting used to, you have to fly the plane to the ground otherwise it'll either float forever or suddenly stall if you slow it down too much. This plane could, I guess be compared to a mid wing as it has neutral stability, i.e. the CG is right in the center line of the wing and will therefore just go where you point it. Not too difficult to get used to especially as the plane can fly slowly....

I'm currently putting together a Tiger 60, this looks like a good option as it has the ability to be easily converted from trike to taildragger and has a good reputation as an easy flying sport plane. Although it is a low winger, the fuselage has a low profile (not too much fuse area above the wing) so hopefully it should not exhibit those 'negitive roll stability' problems...

In short, if you have the budget, here's my suggestion: get an Avistar for the equipment you've got and get a new engine, radio, plane package for your next project. You'll probably not want to use that LA engine for a higher performance sport plane anyway...