I also use the GM performance exhaust but on a Alpha. Sounds great and only $200 on ebay NEW.

 

I did a little research into the exhaust systems from around 11 different shops and 1 performance custom shop. The consensus is that for what I am looking for ( low rumble, no street racing sound, easy to go uphill, no reduction in power, still a quiet cab ride, and maximum efficiency of air from engine) is the mangaflow system. The magnaflow system is the most installed out of every shop on the hummer h3 due to its efficiency, lifetime warranty, and fits to h3 without welding to the actual h3. To make an actual custom made true dual exhaust with out a cat back will be tacky and I'll advised due to the smaller bottom of an h3 compared to h2. It can be done, but you won't get that much more efficiency out of it and double the price. Hope this helps..... I will be installing the magnaflow system soon. If anyone has any questions let me know so that I can ask. I will post pictures

 

a recording of the sound would be awesome!

 

Let me see what I can do for the recording.

 

Skikidnmu,

The GM Performance Exhaust isn't too loud. It has a really nice sound. I haven't heard the other ones in person but I was worried about the sound too and am very happy. If you want I can record a video w/the sound for you to see. Just let me know.

Hey I'd like to hear what yours sounds like. I too am thinking about different exhaust options for my H3.