i would recommend getting a Mac Prochamber (what I run) or an X pipe.
The X pipe makes it sound pretty smooth, somewhat exotic sounding, but still recognizable as a mustang.
The Prochamber makes it sound deeper and still very different from your typical flowmasters, but still sounds like a mustang.
An H pipe and magnaflows sounds very deep, but also raspy and unrefined (not a clean sound). IMO it sounds like a beat up truck with rusted out mufflers, doesn't sound like a mustang at all.