Just to muddy the waters a little more, there's the Bassani B4 to consider. It's a 2-1 and sounds a lot like the S/C/S-4. Bassani has made the B1 for a while, and it's for larger and highly built motors like the Dragula. I got the new B4, which looks identical to the B1, but has the less radical headers. It's designed for more low end torque and milder engine builds.
I love the sound, and like NorthGeorgiaHawg said, the reversion rumble is amazing on the B4, too. Quality so far is excellent, and it's definitely not as loud as the D&Ds and Thunderheaders. As far as performance, Bassani has a good reputation, and my butt dyno felt a nice improvement. Need to check the numbers on the dyno some time.
A big reason I opted for the B4s, though, is the looks. The headers curve to accent the transmission side cover before merging into the collector. Thunderheader, D&D, V&H, and Drago headers are all straight through to the collector. The B4s are unique in that regard, definitely stand out. Also, the exhaust tip is contrast cut, which I wanted to begin with. I paid less than $600 through a local shop.
FWIW. Good Luck.