It will really depend on how big a speed freak you are.

Two .25's should give you a little more than the old motor did. It is not because they add up to moe size as much as it is the disc size of the props.

If you fly from a grass field then you wont have to worry about 40/50 class motors on your bird and not being able to sit still at idle.

I learned on the Tiger 2 a long time ago (unless my oldtimers has kicked that is the high wing trainer) and it is a great bird.

If you go with the 40/50 it might not be a bad idea to put flying wires on the tail and that will help to get the CG back when the motors move it forward.

This bird is not going to be a floater any more but that will help you when you get away from trainer style planes anyway