Marr goes for lots and lots of effects. For a guy like that a GT100 is quite workable. I still dig his whole ouevre though. A GT100 used properly can provide standard effects like chorus, phase, flange, delay, autowah, reverb quite decently with the ability to make presets, which allows him to get his sounds he got from traditional pedals without having to tapdance as much. But at the end of the day a GT100 going into a great tube amp is going to sound better than it going into a lower quality amp, tube or not.