I'm with JimmyM - a wall of Marshalls or a wall of SVT 8x10's is part of 'rock'n'roll presentation'... now, you don't have to be into that, but if your band considers itself to be a rock'n'roll juggernaut, then pointless or not, you have to have a rig like the Manhattan skyline
I use two Marshall 4x12 guitar cabs stacked, each reconed with 4x 150w Eminence speakers... the type used for PA's etc... so I think you can see what side of the fence I'm on... I don't need all that power, but it's nice to have something in reserve, and the sound of 8 speakers all with very slightly different voicings makes for a thick, wide sound you don't get with a single speaker
not for everyone, but once I've helped haul in the PA speakers, the drums, the desk, the PA amps etc, a few fairly light Marshall cabs aren't such a big deal... might as well come prepared... i'm considering another 2 412's, but it might be getting silly