That's nearly entirely a matter of personal opinion. Youtube is your friend on this situation.
Muffler: My vote you be magnaflow. "Flowmaster" 40's will be loud and gorgeous, but they'll drone and they don't actually flow better than stock. Flowmaster 50's are slightly less obnoxious. Glass packs are cheap as dirt, but I think they sound lousy on v6's (personal opinion).
Turndown/tailpipe/dumps: if you're looking to increase your interior noise level, consider swapping you tailpipe for a turndown. Aiming the exhaust at the ground will reflect the sound into the cab, instead ouf straight out the back. If you wanna get crazier, dump your exhaust before your rear axle. One of my buddies WS6 is dumped there, sounds amazing, but it's lound enuf to make my jaw hurt.
Like I said, it's all personal opinion...
