the product linked in that thread specifically says compatible with pre-2003 accords...different stereo, I assume?

Most car stereos have aux RCA inputs in back, usually for an external CD changer. Not having taken mine apart yet, I don't know what the OEM accord stereo has, esp. since there is already a changer. There should be something back there, since Honda has an MP3 player option and needs a way to hook the audio in.