#1
hi, mega noob question. FOR SAY... i had this

1. mesa triaxis pre amp
2. mesa rectifier pre amp
3. marshall jmp-1 pre amp
4. mesa 2:100 power amp

can i power all 3 pre amps with 1 power amp?
#2
I don't know much about this but I'm pretty sure it will work
#3
2 pre-amps would be easy since it's a stereo power amp, however if you want more than that you will need either a switch or a line mixer.
A metal band?
Gear:
A Guitar with an LFR > Korg Pitchblack > Behringer EQ > Hardwire CM-2 Overdrive Boss SD-1 > Hardwire CR-7 Chorus>
Orange Tiny Terror >
LzR Engineering 212 cab

My other amp can run Crysis
#5
http://www.rjmmusic.com/minilinemixer.php

I'm presuming your going with a Midi setup, so a decent Midi controlled switching system should get your signal routing to the preamps well situated. If not, consider the Voodoo Lab Amp Selector or the Lehle 1@3.
ESP LTD EC-256 and a Fender Deluxe VM