They should, I left some room on the top of the amps where air can flow through. When I had everything temp set up, the MS8 and the two amps were all stacked on top of each other with no problems, so I think they will be fine.
Ended up going a different route for the amp rack. It was too cluttered for me and I still needed to add another amp, and little more trunk space is nice.
Looks like a mess but it about as clean as I could possibly make it and it is 100% better than before.
Long-time no update... did an install on a members car and he brought a sheet of 1/4" mdf we didn't end up using, so I finally went ahead and used it and re-mounted my horns.