To be honest I think real 350 owners are not going to be "upgrading" to the 370z, the power difference and styling is just so minimal it doesn't really justify the extra costs. Well thats my opinion anyway.
You can get some excellent deals on <2007 models at the moment, I bought mine in February and I recon i have lost around £2k already, I don't care though as I'm keeping it for a few years and i'm having too much fun.
R