I'm also in the market for aftermarket mufflers, both of my vans need new ones.
After a little bit of digging around I think I am going to try out the
AP Exhaust Enforcer II Steel 2 Inch Muffler 3742 that Summit sells for about 26 bucks.
It is about the same length as the stock (on my 91 NAs, not sure about the late models/SC mufflers) though a thinner diameter. Stamped cartridge style internal baffling.
Reviews report the sound as being quiet, which is what I'm looking for personally. We'll see how that goes.