i've been looking into dual exhaust and all these different setups for months now. You seem like you want exactly what I want. Super 44s, true dual, cats still on.
I've heard that, and don't quote me on this do more research, that the 87-93 GT catbacks fit our cars, except the hangers are different. This is good for v6's because the 87-93 GT's have turndown tips at the bumper, which complements our problem of not having cutouts. Also, there is not a super 44 catback for 99-04, only super 40s which is lame. HOWEVER, American Muscle sells a 87-93 GT catback exhaust with super 44s for $370 (cheaper than the 99-04 GT catback with the wrong mufflers.)
As for the H-pipe, someone told me that you can buy a "universal" h pipe from jegs, not sure about that (its $50)
Or you can buy the h pipe adapter sold at american muscle that is designed for 99-04 v6's. It says to cut your y pipe and it bolts on after your cats. It allows you to install any 99-04 gt catback, but if you are having an exhaust shop do your exhaust, I doubt they would have problems bolting on an 87-93 GT catback anyway. This method allows you to keep your stock cats (which is good for v6's i hear, w/o cats=
Edit: final cost of parts can be between $400-$500