Dan, the bottom line is that if you want more performance via an exhaust upgrade, and I mean one that is actually NOTICEABLE just from driving the car, and not merely a 5 or 10 HP gain which will only be detected on a Dyno, then you're gonna have to reduce the overall flow restriction in the exhaust, and that means it will also be louder too. There's really no way to avoid that. More performance also means more noise.
Sure, you can get rid of some of the exhaust flow restriction by simply going w/the headers, and that will not make the car all that much louder, if at all. But don't expect any gain in acceleration, unless you go the whole 9 yards by replacing everything w/the exception of perhaps the tailpipes. W/the stock mufflers, I doubt very much you'll get enough of a power increase for you to notice just by driving the car. You'll only see such small power increases on the Dyno.
My suggestion is, that you either stay w/the car being quiet, or you go all out w/the exhaust. Don't half-step. If you do, then you'll accomplish nothing, and therefore you won't be satisfied. But as far as your Trilogy comment, keep in mind that if you really like the car to be quiet( I don't), then you can Supercharge the engine w/out performing other mods such as an exhaust upgrade, and you'll be satisfied w/the acceleration increase.