The tC is one hell of a car for the money, huge performance potential, very very well made, could be an excellent horn, dash mid/tweets, mids in doors with pillar tweeters, kick panel two or three way(midbasses in doors, etc, etc, car, room for whatever you want to build!
I have Lotus Refs in my doors, just cut the center out of the stock baffles, beefed them up a bit and I ran a diagonal brace inside the door accross the mounting area for the speaker.
The car has fairly high road noise, odd considering how well it is treated by the manf. The main problem area is the side panels right behind the drivers doors, beside the rear seat. It is a very large and not well supported area, I could flex them in and out at least 3/8" on bass(Arc 10, 1000 watts

Since our car will see alot of autocross action I did not want to just add a bunch of mat, it would of taken at least two but probably more like three layers in the middle.
Instead I bonded thin wall aluminum channels to the outside skin(inner side of course

every 4" aligned horizontally as long as I could make them. It is a bit tough as they have to be formed to match the body contours. Then I ran veriticle strips of mat 3" wide, every other 3" over the area and where it intersected the channel just worked it down really well onto the sides of it then cut out the area what bridged the bare side of the channels. Then I used a few patches of ensolite and after than covered the whole area with a 2" thick piece of accoustical foam.
After than I filled in all the voids in the area with expanding foam, not garden store stuff, this was commercial grade, very good foam. I also covered the majority of the wheel wells with it, some areas are double walled, not needed there, they will just get ensolite on them.
Then, I filled the hollow area above the wheel wells and the outside of the car with expanding foam, in several sessions to allow complete expansion each time to prevent any body damage.
The rest of the car is filled with foam as well, all body cavities that is, Pillars, crossmembers, frame rails, etc, etc. We used over 200 liquid oz of expanding foam in the project, will drive it for the first time today, just around the block, tomorrow it goes on a trailer for moving to our new location.
We removed all factory deadening and are using our products of course as well as several other items like silicone sealer, tie wraps, double face tape, etc, etc, no stone left unturned. That is about 3/4 of the sound deadening we have done, still have a few things left to finish up, nearly 150 hours so far
Anyway, I drifted off a bit from the post topic but though you may want to see how far an anal retentive sound deadener can get carried away with, lol!
Rick