I will relate some stuff that I found out in the process of doing my NX2000 regarding mufflers and noise level.
One thing is that yes, while the turbo itself actually does quiet it down a bit, it is still loud as hell if you have a short muffler or no cat. My NX had a 3" cat, and a 3", 12" diameter muffler and it was almost loud enough to make your ears bleed. I mean it was really, really, unbearably loud. So I had a muffler shop weld in a 3" dia. glasspack midpipe, which besically took the edge off, but it was still too loud IMO.
The secret to keeping it quiet is getting long exhaust components. For my current project I'm getting a 20" glasspack midpipe, a 17" cat, and a 19" muffler, all 3" diameter and it will all have 3" mandrel bent piping, and a 3" downpipe as well. I believe this will allow for plenty of throughput while keeping the noise level way down. I really hope it will be fairly quiet actually.
Ryan's car doesn't sound too bad, it's definitely livable, and quieter than a lot of NA SE-Rs with bigass mufflers, and I think his muffler is 20" long.
I'll be blabbing all about it when it's finished anyway, so I'll have a better idea of just how effective it all is when it's done.