I myself have Flowmaster Super 44's. They are LOUD (when gassin the floor). At idle it has a smooth deep bellow. They go for about 70-80 a each (which you need two). Go to any local muffler shop and they'll cut your stocks and weld your tips onto the new exhaust for between 50-100 depending on the shop. As far as diameter goes? it REALLY does NOT matter, they can fit weld adapters to fit your size. Here's a video to help you out with sound wise if you have the 4.6L N*, BUT KEEP IN MIND... Mine is VERY LOUD because the cat is deleted. So please take that into consideration.I have 97 sts and I was wondering what sounds good and what size inlet and outlet I need to get.
My Flowmasters are 100% stainless steel and came pre-coated straight out of the box.... im getting lost at the part your saying aftermarket isnt high quality? IDK about this reply, but when i see someone asking about "whats the best sound?" i automatically assume like all car enthusiasts... what would sound more aggressive, what would sound "badass", etc. I humbly invite this poster to please correct me if my assumptions are incorrect.For a Cadillac a quite muffler is what sounds good. A loud muffler belongs in a 4 cylinder Honda.
The best mufflers for your car are OEM (quality and performance). Anything else is just noise, plus you will have to change them every 2 years.
Unfortunately OEM mufflers were LONG discontinued, the price was less than $200 for the left one and ~$750 for the right one (as is one assembly with the silencer).
The ONLY direct fit mufflers for your car are made by Walker. The price is ~$120 (check www.Rockauto.com) but you will have to separate (cut) the right muffler from the silencer (in a similar way as the left one is mounted from factory, you will see as you look under the car what I mean).
The Walker Quite Flow are pretty close (sound wise) with the OEM system. Since no amount of money would got me the OEM mufflers I had to compromise and install these Walker mufflers.
Again OEM at least $200 Walker no more than $120 so that tells allot about the quality. I painted the mufflers with 3 coats (i.e. 3 cans) of high heat paint when installed and so far (almost 2 years later) so good.
But when these Walkers will fail I will buy Deville OEM mufflers (still available). Only the pipe with the tips (and the tips) needs to be modified (Deville pipes and tips are shorter). At least I have the peace of mind given by the OEM parts.