I need to mount two amps together. One on top of the other.
What is the easiest, best way to do this. I also need to keep them as tight as possible due to space limitations.
Any suggestions?

use small tubes to run long bolts through the mounting holes. keep in mind that you want a little room for air flow to keep tha amps cool!

I personally like threaded hex standoffs. Clearance for a machine screw through the base to tighten the first amp(through the backside) then other amp on top of the standoffs and bolts through the top. Nice and tight.

Robbie did something like what Ray said. Used small diameter threaded rod with pipe as sleeved spacers between the amps. Worked well.