In the end its a matter of personal preference. I also own a P-120SE and it is a kickass engine. If you have the spare cash, you should probably go for a 120 size engine to use it on a bigger bird later on. Talk to the guys in your club and see what engines they are flying. That can help if you need assistance later...

About the Panther and 80N - it is absolutely sufficient for scale flying. The Panther was no rocket and should not be flown like one. You can easily go with 1/2 throttle and do all scale like maneuvers easily. It will still go quite fast on full throttle. After 7 1/2 minutes of flight, I only had the two saddle tanks empty. the main fuel tank was still full.