The Panamax 4310 and 4400 have voltage sensive 12v triggers so you can turn on the outlets to the amp via this trigger. Unfortunately, that means all outlets on the unit, so you wouldn't be able to plug in anything that you wanted to go into standby (with memory) on the same unit. The 5100 has a separate bank that can be turned on this way, but again, anything on that bank will also get turned off, and we are talking $200-$300 price range too.
Take a look at them at
www.powersystemsdirect.com
Since your amp doesn't have a stand-by mode, it is probably OK to just leave it on all the time.