I should relate one bit of advice when running multiple Guitar Amps in a large room / concert hall.
If you do not manage the acoustic phase cancellation that physically occurs due to multiple Non Time Aligned Audio Point Sources (i.e. Multiple Guitar Amps spread across a large stage in a Large Concert Venue) , you may find the audience will report that your Live tone sucks compared to the opening Acts Guitarist who only used one 1965 Fender Deluxe Reverb close mic'ed with one Shure SM57.
More technical discussion on Audio Time alignment is herehttp://sound.westhost.com/ptd.htm
True, Many classic Guitar tones we all know (Brian May) are the result of Multiple Guitar Amps miced both near and far which creates phase errors in a controlled studio environment = thick tone provided the resonant tone does not conflict with the key of the song - but its important to have the same tools / knowledge to tune your Live rig for the specific venue.
On the cheap, one method is use a Yamaha 01V Mixer as a Guitar "Pre-mixer" - before your FOH Board feed.http://www.soundonsound.com/sos/jul98/articles/yam01v.html
Each night, be sure all your Guitar Cab mics are consistent: set at the exact same distance / position relative to the speaker.
Run every guitar amp mic into a separate channel on the 01V , then employ the individual "Channel Delay" controls on each channel of the Yamaha Mixer to assist with restoring time alignment and minimize the Phase cancellation for all the guitar amps in that specific room.
I see band Riders for touring bands , and many do specify "Yamaha Mixer Only" - for this specific reason, because bulk of Mixers lack the unique Channel Delay controls
that are built into most high end Yamaha Digital Mixers.
But know that most Professionals who are reading here understand all that - been there, done that, bought the T-Shirt.
and in 2013 many major acts have opted / or have tours managers who insist the whole band USE no onstage guitar amps, and In Ear Monitors for the whole band with better management of all stage audio sources to allow the FOH Mixer more complete control over the bands Live sound.
The biggest compliant most FOH Mixers inform is lack of ability to "Turn Down the Guitar" when confronted with acts with guitarists with large multi-amp rigs.
I also recommend buy PlexiGlass Shields to place in front of the guitar cabs, to assist your FOH Mixer's job, and improve the audiences's opinion of your live act, and sell more CD's.http://www.thegearpage.net/board/showthread.php?t=1055062