I have a 156 GTA and a 3.0 166. I also had a 3.0 GTV before. The GTV is more like the GTA (I.E sports car).
I believe the 3.2 166 is like the 3.0 166 with a bit more grunt....
My 3.0 166 has solid flywheel/gta clutch/quaife diff, and also eibach sports springs and koni fsd shocks (along with suspension overhaul and wheel re-alignment and engine re-map).
These upgrades I have found do improve the 166 but they do not make it into a sports car.....however, if push came to shove I'd keep the 166 over the GTA for its all round combination/compromise...! However, having said that, the GTA is a heck of a car....it amazes me that anyone would want to drive round on public roads with anything more than 250 bhp.....these 500bhp saloons with all their techno wizardry....when do you get to use that power? The GTA has to be kept on a leash 90% of the time.....the 166 is a happy compromise for public roads....and as **** said still needs a track to safely explore its full potential.