New answers tagged headphones
There is nothing in your described signal chain that depends on powering-up order. It's entirely and completely irrelevant. As a side note though, get in the habit of turning your headphone volume down/off when you take them off your head, and turning them on/up only after you've powered everything else up.
Something like this may be useful http://jamhub.com/bedroom/. You can connect multiple instruments and create multiple independent headphone mixes. DISCLAIMER: I have never used it myself and it's not intended as a sales pitch.
Top 50 recent answers are included