If money is the issue then I would seriously look at the Thunder Tiger engines. As an instructor I found them to be as easy to adjust for reliable running as my OS engines and they have very good power. I had an OS 40FX engine on my LT40 trainer. It worked but when the grass was tall, it made for some very low speed takeoffs. As someone above wrote "Sometimes the LA engines barely have enough power to get the plane to move through the grass fast enough to takeoff. Not so with the AX." < I totally agree and it was much easier to train with LT40's that had 46FX engines pulling the plane. The AX engine is the newest version. BTW, the Avistar is actually considered a very capable second type plane because of its speed range and aerobatic ability so you may just want to hang on to it even when you get another plane. It will fly circles around standard trainer type planes.