I would imagine that it would not be that easy to get 250bhp out of the sigma 1.6. My feeling is that you would finish up with a track day or race engine that would not be that practical for road use: not much torque at low revs. Also to cope with that output you would need to upgrade the wheels and tyres.
I quite agree, Peter. My 4/4 doesn't have a Sigma engine, but at 165bhp I feel it gives plenty of usable performance that doesn't overwhelm the chassis and tyres.
I prefer a car in which I can drive enthusiastically and in which I can provoke a power oversteer when I try, rather than a car in which I'm always having to be careful and might power oversteer if I'm inattentive.
