In an attempt not to repeat what everyone else has already said. (though I do agree with almost all of it). There's one brand that has been overlooked in this thread. And let me just say now that if someone did mention it and I missed it my apologies, but I'm talking about Evolution.

Evolution engines are sort of the new kid on the block, but they are producing some fantastic engines. I own two of them and if I ever buy another 2-stroke (parrish the thought) I will be looking in their direction first, although, my 4-strokes are and plan to remain O.S.

You can pick up the Evolution Trainer Power System (which is essentially a .46) for about $80.00. And if you want to know more about it you can check out the [link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=153]review[/link] by Mike Buzzeo (shameless plug)