I also had an 04 g 35 sedan w/all options. I now drive a '11 g37sedan 6mt. The differences are huge. We are talking night and day here. A bump of almost 70 horses, tuned steering, technological advance, etc. However, this model is old and will be replaced within a year. Maybe you can wait or just pull the trigger and get an '11 that will be considered the "older" model in less than a year.
Another consideration to think of. I owned the '04. I did not have any payments to make, it was mine free and clear. Now I have a much nicer car but not I am paying monthly payments. Makes me think about all that money I am spending each month. It's like buying a new ipad every month!!!

 

Don't remind me! When I think about the big number I started doubting its going to be that much better. I'm also doubting if The limited is worth it when I can buy a used 10 or 11 and customize it a little to make it look as tight if not better. Of course the challenge there is finding an xs model.