I have a single exhaust. It took a little experimenting, but I finally HAD something I liked. I went with 2-1/2" aluminum, straight through a single Dynomax Bullet muffler. It made a bit of power up high, and of course, lost an equal amount down low. But it was pretty loud and raspy. I mean, REALLY raspy. I only drove it like that for about 10 minutes. Just long enough to get to Kragen, to get a Cherry Bomb, which is currently serving as a resonator. This setup was pretty nice. It sounded good. Even at high RPM. But then, I got my SS y-pipe. I found a lousy combo here! It is back to raspy again. It's bad! Once I get past 4500 RPM, it sounds pretty damn nice, but that mid range sounds ******! Plus, the fact that the SS pipe coupling (or the way it was put on) destroyed the front part of the pipe. The donut gasket dsintegrated on one side, and the pipe (aft of the coupling) has a crack 2/3 of the way around it. This does not sound good either. So tomorrow, I should be putting a different resonator and maybe a ****** muffler on, and hopefully getting the crack fixed. I'll let you know what it sounds like, when it's done.
Some people (I won't mention the SHOps name) say that I will lose power without the 2-1-2, but I figure that once the exhaust is in one pipe, it can come out one pipe. And as you probably noticed by the fact that the muffler is hidden, I'm not one for a big flashy exhaust. A long as it works, and sounds good. One of the things that I had going for me, was the fact that my mufler shop was willing to work with me, for trial and error. (mostly because he was a Huey crewman, and I walked in in a flight suit)
Good luck, and let us know how it goes.