Ok - well, to tell the truth, the easiest way (were it me at any rate) to do this would still be to use the remote turn-on output from your head unit but put the switch inline on the remote line.
Ergo: Remote Turn-On Output ---> into one side of a switch / the other side of the switch ---> to the remote activation input on your amp.
This way the amp would still only work if the deck was on while still giving you independent control of it. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif