I'm looking into a resonator as well, and I have found that the Flowmaster Hushpower II is a pretty good choice. I think it was built with more of a V8 emphasis, but a few people on r3v liked them. Plus they are stainless and only $90.
Out of curiosity, what is the best resonator to get for our cars (I have a noisy Bosal exhaust) to get a deeper sound, including the original piece?