I would think the MTXs could handle it down at 1 ohm. I don't know about the new subs, but their old stuff was underrated and from what I have seen with most PA stuff, it is a bit overrated.
As long as he has clean power going to the amp and doesn't go crazy with the volume, bass knob, and keeps the rca signal clean (set the gain with a multi-meter), he shouldn't have too much issue.
Just my $.02