Performance-Curve. com for cats, not advance auto or autozone. You can get a spun stainless cat for something like $60-70.
No stainless mufflers that I know of that are as quiet as stock, but my Flowmaster Super 50 Delta is merely rumbly (video with sound in my build thread). Their 60 is a little quieter but only available in stainless as part of a whole cat-back iirc. Their 70 would probably be really close to stock quiet.
Magnaflow's stainless mufflers is also tasteful sounding to most, but not stock quiet.
Build Thread -- http://www.jeepforum.com/forum/f177/whats-chrokeese-build-thread-2525690/