You thought about a Scorpa 125f? With a few minor adjustments you can get plenty of power out of them. Fairly cheap as well.
I'm looking to sell mine fairly soon actually, I've got to the stage where I need more power now, the 125 is awesome and I love it to bits, but I just need that extra bit more power. Been looking at the Scorpa 250f's, but they are quite expensive, might just try and get a 250 2t instead. I've also got this that I might sell too to fund a new bike. But again this is mad fun, it's so awesome for just playing about on.