I am not sure as to the benefit of swapping in a six speed into a tC other than bragging rights. The tC engine has enough torque and power across a wide range of rpms -- from low to high. You don't have to rev the engine to the extent you would in say a Miata, s2000, or Celica GTS for it to get up and go. These other cars have high strung engines that perform well at high rpms but slumber when you keep them low. The Celica GTS VVTi kicks in at something around 6000 rpm, nearly the redline of the tC, if I recall correctly.
Anyway, the main benefit of a six speed transmission is to keep the car in that small powerband of rpms in which the engine produces the most power. The only other pratical reason I can see for a six speed would be for the additional overdrive gear for highway driving. This high gear would let your engine rev very low for increased fuel economy.
The thing with 6-speed for the tC is that our 5-speed is geared like most 6-speeds, except we don't have a good cruising gear. So the *only* reason for a 6-speed would be to achieve better fuel economy on a highway - that's it. And if you do simple math as to how much would you save on gas vs. the cost of the swap / losing warranty, I'd say who the heck needs this stupid sixth gear?
If you don't believe me about gearing - do a comparison of tC's final drive with any 6-speed out there...
^^ I agree with you on that one. Sure a 6 speed sounds more enticing and that overdrive gear would sure be nice, so I'm not up to around 4000rpm at 80mph, but I just can't see the gas mileage savings justifying the cost of buying and replacing a brand new tranny just for that.
Thanks for the input guys, I am only thinking of this in consideration with the super charger. As I thought it might be more valuble to keep it in the seperchargers Prime rpm level. But it is just a thought. All things will have to fall to gether after the super charger comes out.