It's a very good suggestion - I've seen it mentioned before and forgot about it, although now that I think about it I think it's even included in some of Outlaw's amp manuals. Here's the blurb from the Model 7500 manual:
If your processor or receiver does not have a dedicated trigger jack, it is still possible to activate the unit for automatic turn on when a Switched Outlet is available on the rear of the source device. To control the amplifier in this fashion you will need a small AC to DC power converter, capable of delivering a 6 to 12 volt DC signal. The DC voltage should terminate in a standard 3.5mm type mini plug. This type of converter may be obtained as a Power Adapter from many electronics retailers.
When installing, press the Main Power Switch on the front panel of the amplifier in so that it is in the ON position. Plug the AC adapter into a switched outlet that will be activated when you wish to have the amplifier turn on. This may be the switched outlet at the rear of an AC receiver or other audio equipment. Connect the 3.5mm mini-plug from the adapter to the trigger-input jack on the back panel of the amplifier. The amplifier will now turn on and off automatically, based on the status of the controlling device.
I'd forgotten about this trick, but it's definitely an option in your case, mgdurand. It might be worth a trip to Radio Shack to see what you can find.