(Hopefully) my final comment this makes interesting reading:
Bedford Times
Gumpert Apollo S - 1:19.40
Caterham R500 - 1:20.20
Ariel Atom 3 - 1:21.50
Brooke Double R - 1:22.50
Porsche Carrera GT - 1:23.30
Porsche 997 GT2 - 1:23.50
Nissan GT-R - 1:23.60
So we have a mid engined racer followed by a front engined kitcar, followed by a mid engined kit car etc. The CGT is 0.2 of a second quicker than the GT2 and 0.3 than the GTR. This would suggest to me that it wouldn't take much work for a GT2 or GTR to be fettled to be quicker than the CGT. Given that these three cars have similar 'ring times (ie close) that would suggest that it wouldn't take that much to bring either the GT2 or GTR to the level (if not quicker) of the CGT. Perhaps the PDK gearbox on the GT2 would shave a couple of tenths off it's track-time. Perhaps the v-spec likewise. I fancy that one of Herr Ruf's cars would also be quicker than the CGT.
Which of these cars is the best? That purely depends on best at what. The CGT is certainly the most impressive (v10, carbon bits, odd coloured wheel nuts etc). The GTR or GT2 are better for rear passengers (not much better mind

).
Any car with enough time and development can be quicker on a race-track than any car. A Corvette C6R is quicker than a F430 or Murcie at Le Mans. On a b-road a WRC car would wipe most things out. Does that mean my neighbour's Ford Focus is better than my GTR?
Unless anything interesting turns up I'm going to shut up on this topic.
Cheers
Cris