if you want a stylish exhaust in that price range then look at
ARK or
fast intentions. Here is a link to the video with headers and test pipes, if you do not get headers or test pipes then your will sound like the second link i posted. ARK also provides a stock looking CBE. If you want to keep a stock look but improve sound quality then you could look at the
stillen and [B]
berk exhaust.
YouTube - Destiny (370z) ARK CBE
YouTube - ARK PERFORMANCE EXHAUST SYSTEM NISSAN 370Z GRIP TRUE DUAL Exhaust SYSTEM TYPE 2
You can youtube any other exhaust that i mentioned. If you would like to go a cheaper route and make the stock exhuast just a bit louder but keep the same note the I would like to mention HFC's as a possibility. I hope this helps.