If your not in a hurry, Pypes performance exhaust is coming out with full systems ( headers to tailpipe) for a bunch of c3 years. Supposed to be out in spring time (2006).

 I dont have any experiance with pypes, maybe someone else on the forum knows about their products,quality etc. Might be worth the wait.

 My question is which mufflers give a good flow without drone/resonance in the car

I have the Hooker AeroChambers, and love the sound.  They are borderline too loud, but not over the border.  Great tone.

I'm surprised BORLA mufflers are not on your list. Those things are built like battleships. The Turbo universal muffler number 40659 should fit about the same as stock, or the Turbo XL is a little longer but should fit with slight modifications, number 40665

I am a big fan of The Walker Dyno-Max welded body mufflers. Mine are 2-1/2" on full length Hooker headers. You can see straight through the perforated pipe through them, but they are fairly quiet for cruise, but really RAP when I shower down on it. Sounds pretty mean.

Dave

Go with the chambered exhaust. I promise you'll never turn your radio on. No tune sounds better than those pipes talking trash. not to mention the view from the guy behind you.