To get even 200bhp from a 20v n/a you'll have done extremely well, specially since there are 2.4 converted n/a's running around 190bhp, to crack 230 you'll need more than throttle bodies.
We were going to build a monster n/a project a few years back, my dad got hold of a vis lump from a bravo hgt, that had c+b cams, and was mapped to 189 bhp on a piggy back ecu. The plan was to fit and throttle body that engine and take it from there, unfortunately it never happened, as our 20vts became the main point of focus, and still are...it's never ending!!
I have however recently bought a n/a that's ripe for a project, I'll be starting shortly...if only I knew who to bribe for a set of cams
Anyway, I vote 20v n/a any day! Regardless of what will get more publicly, a 200+ bhp n/a will be an unbelievable drive, and imagine the sound! And that raw n/a power and responsiveness taken to another level on Itb's! Not to mention coupe looks vs panda!
I'd say:
Stilo 2.4 bottom end
A considerable amount of head work
Columbo & bariani cams
Throttle boddies
fancy exhaust system/ Inc custom mani
And some good mapping on a stand alone ecu should get you close.
I think you should go for that, too many pandas have already been done, there's a few t-jet ones over here running 160-200 and a couple in Poland (t-jet crazy over there!) The 160+ t-jet ones ive seen are more than quick enough for the road, and you certainly wouldn't want to crash one! I think 250bhp in one of those, unless you plan on belting it down the 1/4 strip, will be fairly pointless.
200+bhp n/a's I know of however = none! Get it built