Why bother swapping a 2.0 engine in, I'm making 230hp now with the 1.4, and I've still got some more tinkering to do, I don't think 250 is at all out of reach.
The point, to me, of the Sonic is that you're running a nice little car with enough of an engine to get you around without so much engine that you're wasting a ton of fuel just keeping it idling or barely ticking along at cruising... but with the turbo power to kick you in the backside whenever you really want the go juice.
A 2.0 would be exactly the wrong direction for my purposes, although I'll grant you someone who was interested simply in power as opposed to the more complicated "power when you need it, eco when you don't" angle would see it otherwise.