I've been worried about having a system with that dreaded drone, as well, so these were my thoughts on setting up a louder aftermarket system that isn't too obnoxious.
Do you have an h-pipe? I'm not sure how an h-pipe would work on a y-pipe before the resonator and whether it would tame the sound down (and especially on a system with the mufflers right at the back of the car), but I know that on my 3.8 Stang, i'd done the exhaust as true 2.5" dual with a MAC catback, and the drone was pretty bad. After i'd put an h-pipe on it, the drone went away and it made a twangy sound into a lower, more sinister note (in the lower RPMS--at higher RPM's you can still tell that it's a V6). The best way to describe it was that the muffler sound had seemed like it was coming from the tailpipes, rather than the middle part of the car, which was where the mufflers also were.
Considering that it looks like my '91 SC shares the same coil pack as my '99 Stang, the engines are even fire, if that helps, and some people have suggested that for performance reasons in being an even fire engine, the Ford 3.8 doesn't benefit from an h-pipe like an odd firing engine would. Even though the engines are even firing ones, i've still experienced a much better exhaust note with an h-pipe.
Has anyone done true duals on the SC's, and have they had any experience to report with an h-pipe before or after the resonator? My attempt at common sense would dictate putting it before the whole system.....because h pipe affects the exhaust pulses, which is why they're almost always put before the mufflers to calm down the rest of the entire exhaust system. Some people say to put an h-pipe before the cats, but any modifications to the pipes before the cats, apparently, may not make it pass emissions.
My other observation is that from the examples that i've seen online from guys taking off their cats on Ford 3.8 engines (and/ or using an X pipe), it yields a much louder sound, but with a raspy, buzzing, unpleasant note. Longtubes give a deep sound, but in a more open system (no cats), they seem to also amplify the worst aspects of the engine's sound in the higher RPM's, almost like a "lawn equipment on steroids" sound, where it sounds great at idle, but terrible as you accelerate.