I had an '05 and the 370 is a huge upgrade IMO. No rattles, I think it feels "more secure" when I'm driving. Tighter fitting seats (or maybe I just fill them out more
).
The only thing I miss from the 350 is paint color. I had Daytona Blue and loved it.
The Nismo is not really going to give you much more "oomf". It's built with better handling, etc. More track friendly.
Gopher it. Don't be scurred.