Exhaust improvement question

[finaltable]

I understand that making a more free flowing exhaust will help the performance of my engine (and more important, the 1JZ I would like to put in it eventually.) That said, I do NOT want to have a car that is loud or has one of the obviously aftermarket tailpipes one sees on all the low end Civic/Neons out there; in fact, I want for it to require someone pretty knowledgable about Supra to know that my car is anything but stock.

The other day I was driving next to a Dodge Stealth (the driver was admiring MY car, btw) and noticed that it has two sets of tailpipes where my Mk III only has one. I know that engine is a 6 (though a "V", not and "I") so I wondered if it is possible to double my outbound exhaust channels as well. I realize I am probably stuck with a single exhaust manifold coming off the head but if I could split into two immediately would I realize a similar gain to what I would see with one of the bigger diameter pipes?