UUC's TSE3 lives up to its hype. It is truly the superior system out there in terms of sound, quality and appearance from the rear. I took the advice from other members on the board to spend the additional time saving up and I cannot express how happy I was with this decision. I grin every time I simply start up my 323i. Running through the tach is absolutely unbelievable. Oh, and no highway drone, which was a huge factor for me. Especially with the relatively low-geared 323i.
Speaking of the 323i (I have the same vehicle), the TSE3 sounds, in my opinion, better with our 2.5Ls than on the bigger displacement engines. I bought two TSE3s at the same time to save on shipping, one for me and one for my friend with a 330i ZHP. In making a comparison, my 323i has deeper, burlier sound and when you decelerate, it produces an intoxicating burble, for lack of a better word.
Please take my advice on this and let me know how it turns out!