I was wondering if someone could help explain to me the concept of a dual amp rig. I've heard you can run two heads at the same time into the same cabinet, and it somehow produces an even better sound? How does this work? Does it produce a mixture of both heads overdrive sound? How do they hook up to the same cabinet? I just don't understand how plugging two amps into the same cabinet, could produce a better sound then having one amp plugged in? I thought two amp heads into one cab would sound muddy?

The reason I am asking this is because I currently have a JSX, and I have the possibility to pick up a VHT pitbull for fairly cheap, so I was wondering if I could have my own dual amp rig, and if it'd be worth it?

Any help would be greatly appreciated, thanks a lot in advance!!
Main rig:
ESP Horizon FR-II
ENGL Invader 150
Mesa Traditional cab w/ v30's
ISP Decimator Pro Rack G
BBE Sonic Maximizer 482i

Back up rig:
ESP Eclipse STBC
LTD EC-1000 VB
Framus Cobra modded