it depends on what you want done, for stereo stuff, like i said, i'd go to myer emco, they can get pretty imaginative and it is possible to make a sub box without removing the spare. it'll probalby cost a pretty penny though, that's a lot of custom fab work and it isn't going to be cheap.
for performance stuff, drop me a line, i know a couple people that could you out in the nova area. AAM is good too, Mike's a good guy and they do lots of supra work.