the stock radios in all 03 accords are one piece. There is no way to remove the radio, because you'll lose the climate controls. There would be no reason to send sound from an aftermarket deck into the stock deck... that'd be pointless. If you add an aftermarket deck, it goes below the radio... and you'll essentially bypass the stock deck (eventhough it has to stay there). It does make for a shitty situation... personally if I had an 03, i'd just leave the stock deck and work from there... I would never be able to stand having 2 decks in my dash, with one that dosent even do anything.

I'm sure someome will get creative and make a new faceplate that replaces the stock radio, but leaves the climate control buttons in their places. That would be a total custom job involving fiberglass and everything. And who knows how power gets to the climate controls... weather they're fed from the radio, or they have their own harnesses, seperate from the radio.