All quite interesting to me, I think you have done well to push a 115bhp car so far. I have looked at remaps myself (and tuning boxes) and am still undecided, it seems just a remap takes the 115bhp/250nm to 150/300, quite an improvement, I have noted that the multijets offering 120bhp have less torque and are slower (to 60) than the 8v, so you need to get a 150bhp multi, but they are not too common if you want performance, I'd totally dismiss the 2.4 Abarth as any N/A engine has only limited tuning potential, without spending shedloads on it..ie a 170bhp Abarth gets upto 180 from a map, yet a 150 multi for the same cost map gets past it to 190bhp (the guys I was looking at claim to be able to get 210 from the multi, but wont go past 190 as the 'box diff n clutch won't go past 190 either)
I did read about a guy on Alfaowner who was aimingh at 400bhp from a 1.9 in a GT, but that was a serious and very costly mod list including loads of one off custom parts.
so IMHO
your at the top end for now with the 8v unless you want to throw loads of dosh at it
You could go again with a 16v 150bhp (Oh and you can fit an Alfa Q2 diff in this model-LSD) and push it upto 190, or above if you are happy to replace drivetrain items
I do wonder though whether you could put a 20v turbo engine etc into an Abarth, these do tune brilliantly, and would probably give you the ultimate Stilo-again not a cheap option