use the 12 volt trigger to activate the relay,use the contacts on the relay to turn on the power supply.

i use a 1050 to feed a b&k amp.i have no overheating issues and i just aim a little personal fan at the rack when i do agressive and extensive jamming.(which is what i would do,temporarily,if i was you)

i did have a technics receiver that would shut down from heat,and it had a temp. controlled fan built in.