I haven't played a mark III coliseum, but from my few days before i shipped my mk II coliseum to mesa for service, I have seen the light. It's not about the volume, but that's a plus. It's about the headroom... the tone, articulate, note definition, attack, responsive. not to mention there aren't a ton of them, so if you find a clean one for a deal and have the cash jump on it. especially if it's local. will he let you plug in before you buy?
scott