I'd still go with the OS Max 46 AX. It's $149.99 on the Tower Hobbies website and you can get a $20 off coupon. That would make it $129.99 which isn't too bad for this quality of engine.

Whatever brand you get in the end, don't go with a 60 size engine on this airplane. It will make it quite a bit heavier and it will be grossly over-powered. I have the same size trainer as this one with the 46AX and when training someone, I have to have it throttled back to about 40% throttle so it will fly slow enough for a beginner. At full throttle it will keep up with most all of the other faster airplanes. I don't even like to fly it at full power as you have to turn so often to stay in the pattern.

In the right hands the cheap engines probably run great, but for a beginner, they are not worth the trouble. I had the MDS on my first trainer and even had help from an instructor at the field when I was learning again and they couldn't get it to run right either. They recommended an OS and once I got one I never looked back. You just don't have to mess with them.