iphone 3gs

I am shopping for a loading dock, AV Cable (that works through the powercable plug), and a charging station that wil allow me to plug my iphone3gs into the dock and have the dock wired to my HiFi stereo (not through the headphones jack) and charging from the wall using a pronged outlet charger that will let me plug in the USB cable into the outlet at the sametime. I have found a few cable packages that appear to do both, yet the info on these accessories says they are compatible with the 3g and the 3gs is not listed. Any suggestions? Thanks