The 4* is a great second plane. Years ago I built a 4*60 and put a YS .91FZ on the front spinning a APC 15x6. This motor is supercharged and has the power of a 1.20 4-stroke. It will hover, torque roll, flat spin (true flat spin), fly inverted, do blenders and does the best knife edges for the type of plane it is.

If you are a scale flyer, the a 52 or 56 4-strk would work and work fine, but if you like to 3D some, then I recommend a OS 70, Saito 72, 82 and even a YS 63. Tons of power in any of those motors and you will really love the plane more. Having extra power doesn't hurt and plus you don't have to fly at full throttle. My 60 size with a .91FZ is a perfect combo. For me atleast. I still enjoy flying the plane years after building it. I did add a few mods to my 4*60 such as counter balance rudder, pull-pull rudder, dual elevator servos, 1" addition to the control surfaces, bomb drop door in the front plus a few other changes.

See it here under the RC aircraft section:
http://derrick.myphotoalbum.com