I you want a really good engine for a cheap price get the Magnum .52 2 stroke for $99.99
http://hobbypeople.net/gallery/210760.asp
A guy I know has one in a .40 size Edge 540 T from aero-works it is a great looking engine and from what I can see is real reliable too
you should have a good power to weight with this engine.
4 stroke --> Magnum .72 4stroke $179.99 --- about the same price as the .61 FX
http://hobbypeople.net/gallery/210945.asp