audio out thru dock and headphone cable

so i have an iHome like docking station for my iphone 3g which plays music and charges my phone and i recently received a set of computer speakers and bass that can connect to my iphone via the headphone jack. i had an idea to put the phone on the dock and plug it in to speakers and play through both so i would have awesome sound and it would charge at the same time (also my iHome has a remote to control music). i tried this but it would either only play through the iHome or the speakers. is there any way to get it to play through both. i have an old ipod nano that i guess i could maybe use and my iHome doesn't have anywhere to plug in speakers for audio out. help please. thanks