I am not sure what your expectations were in the "Bose" option, But sounds like you are not very happy with what you have... Fortunately there are several options you can choose to better your sound using the bose amp and speakers, or you may decide you want to overhaul the full system...
Either way Bose system in your 370z is limited to it's capabilities... for some it is more then enough for others it is not adequate... It is your personal experience that counts. But what you are experiencing with bose is with in the norm.
Wicked C.A.S.*::*MAGIC BOXES*::*Nissan*::*370Z Corner Stage1 Package. Stereo system JL AUDIO
Above is a basic upgrade many 370Z owners opt for... No loss of space an much better sound then what you have now. Sports cars deserve a good sound... it makes them that much more enjoyable.