Hi again. You may have already read my response in the other thread..in any case, we've got the exact same scenario almost. So what I do to play along is use a small cheap mixer and/or audio interface, where you can plug in your mp3 source and then mix the volumes out of one of those units and of course your headphones will have to be plugged into the mixer or interface. Besides, you can always find uses for the interace or mixer.. I've now got 3 microphones so it's great to be able to patch them into the system as well as have my mp3's coming through a channel, and my Addictive Drum output. And, the other day, I patched my kid's electric guitar into the interface and even added some fx to it so that it wasn't just straight plain guitar, and we split the headphone connection and jammed "silently" with my stepdaughter's singing into two mics.. was pretty cool. So I'd definitely invest 80 bucks or so in a 4-6 channel mixer, you won't regret it.