I have found that the slightly modified RSX-S does very well with Mustangs when at a rolling start. The RSX has issue from a start as we just don't have the low rpm power. Let me roll along at about 40mph in third, a quick snap to second and it's a blast! From that point it's iVTEC until someone gets scared and lets off the go pedal. I have found that the average driver weenies out at 100mph or so. Either way, it's fun to know where you stand with a V-8, you must respect the V-8 and all of that yummy torque!
Know your Type S and you will do fine with a stock Mustang GT. As for you base RSX owners, especially the auto's... even I ignore them when they want to play.