So I've had my 370z 40th Anniversary edition for a few months now and although the Bose system is not bad it lacks, in my opinion, some bass. I've read a few threads about rewiring the existing subwoofer to include an amp etc but then you can get into issues with where to locate the amp and running new power cables etc.
So I did some searching and found a subwoofer that fits nicely where the Bose one is and it gives a decent amount of bass without being too harsh. The unit I opted for is the Pioneer TS-WS610A. I also managed to wire it up to the existing wiring for the Bose it took me just under an hour to do. The other bonus is that the Pioneer is a 2ohm unit so works really well.
I managed to find a brand new Pioneer from Germany at only £150 including delivery, so it was a bargain and it improves the Bose system no end. I only have the gain on the Pioneer set at half and it pumps out enough bass for me.