plumbing questions

[cowfish]

I wonder if anyone can help me out.
tank-46gal.
I have a 1.25 inch hole for overflow and I wonder if its big enoegh so it wont overflow the tank with a mag 9. and is a mag 9 powerful enoegh so that I wouldnt need powerheads in the tank.
Also what size tube or pvc pipe should I use for return with a mag 9.

any help is appreciated.