So everyone who posted a reply so far talked about the sound of whatever pipes they were proposing. I couldn't give a rats ass about the sound - it's the more free-flowing (and hence potentially more power out of a re-programmed ignitor and bigger jets) that is what I'm looking for.
As near as I can tell, for free-flowing but sufficient back pressure, it's Predators and that's about it. Not clear whether I get sufficient extra oomph out of them to justify the delta cost, so I think I'll just stick with my TORs.
Thanks for the input!