From the amps that he has used, he has several cascading gain stages. The easiest way to get that sort of sound is, number one, get a tube amp that has a good dirty tone, two, get something like a ZVex Superduper to put in front of it, and three, some relatively high gain pickups. If he is using Mesa Triple Rec's, Uberschalls, and now he has an endorsement with Marshall and likes the JCM800 sound, yeah, he is going for a high gain tube sound.
Now, the ZVex SuperDuper is a cascading boost pedal with two identical circuits that boost into each other, and then have a volume knob to keep you from killing your amp. The pedal costs and arm and a leg, but is very easy to build. Either that, or get some boost pedals cheap and daisy chain them to get the over the top sound. It generally works better to use boost pedals rather than distortion boxes, because the dirt boxes will end up sounding like sludge if you chain them together to try to get the amp to overdrive the way you are asking. Anyhow, that is how I would try to get the rig to come close to sounding like his. Either that or start shopping for Uberschalls.
Patrick