I've heard that Tomei Extreme is pretty frickin loud, definitely a higher quality exhaust than the Z1 exhaust. I used an ISR single for a bit, was very loud with Berk HFC. Fast Intentions and Motordyne should also be quite loud (compared with stock), but they can be a bit pricey.

I run FI RHFC and Tanabe Medallion catback, and it's a screamer when I hit the gas (with a beautiful warble, I'll try to link videos sometimes), but doesn't blow your windows out on startup. Most HFC/catback combos will be VERY loud when heavy on the gas, but it becomes a question of around-town volume and pitch/tone that you want when choosing a catback (IMO, most HFC sound the same, and most test pipes sound the same. It's the design of the catback that really changes the exhaust note.

In my experience, from deepest to highest pitched, single->true dual-> single with muffler (stock design). Generally the same follows for volume level. If you want more volume, use HFC/test pipes. If you want even MORE volume, most catbacks will work. If you want the MOST volume, use a single. If you want loudness, the Tomei should give you that


This guys has the Tomei single and longtube headers (essentially really long test pipes, IIRC). If this sounds good to you (does to me!), go for it!

 

The Tanabe sounds great when you get on it but the 2500 rpm drone became really tiresome.