Dan,
I would agree with MSTNGGUY88's assessment of the Thornbirds, way too loud and vibrate too much for what you get. I run the Swamper SSR's, and they're much quieter and smoother on the road, plus they don't flatspot like the nonradial Swampers tend to. I would run the regular TSL's, the Radial TSL's, or the SX's before I would run the Thornbirds, but that's just me. Of course all of those are louder than the SSR's, but they sure look cool and perform well offroad.
On the other hand, a moderator on this site, Paul Gagnon, runs Thornbirds, so I must assume that he likes them. Talking to him might be beneficial to your decision.
A word of advice: Don't expect ANY Swamper to be quiet and vibration free. If you mostly drive on the road and want as smooth a ride as possible, stay with a big name mud tire, like the BFG, Bridgestone, Goodyear MTR, etc, or possibly try the Mickey Thompson Belted HP. Swampers do look cool, and perform very well offroad, but they're not for everybody.