Beausol,
Good advice from EMVIN. If you want 3D you'll want the minimum servos Quique suggests. Otherwise what you suggest would be fine for sport flying.
Servos are like most everything else, you get more when you pay more.
For the money you can't beat the 5945... I'd say it's the best bang for the buck in it's class. Which is pretty much a premiere servo.
The 5645's are nice to with a little more slop in the geartrain and a little slower. But powerful and good quality yes.
You'll want at least a 5945 on the rudder if you want to KE loop and no blowback on hi-g moves...
Call Don's Hobby Shop
http://www.donshobbyshop.com/ (800)972-6273
He offers 4 X 5945's for $75 ea. and a great price on 4 X 5645's too...