Power does not necessarily equal fun..... although it helps.
Empty roads: prefer Lotus Esprit, goes like hell.
Nearly empty roads: prefer Lotus Esprit, goes like hell, keeps catching up with other cars, but can always find an overtake opportunity.
Fairly busy roads: prefer Fiat Cinq - you get longer stretches of ragging it before catching up with traffic than in the Lotus. Roads too busy to overtake either way.
Really busy roads: prefer Fiat 126 - it's a sport just trying to keep up with the traffic sometimes. Only problem is that if you come across a slow truck or something, the overtaking options in 126 are limited, although it's great when you pull it off.
I see about 80 on the clock, although I haven't GPS'd it.