an acura legend deck would not work, as you would need the whole bose system... which would be pointless to swap all the pieces. If you want a clean looking double-DIN, look for a 96-98 Acura TL NON bose deck, it was a cd player and cassette deck in one unit. It would plug directly into your car. Mounting may be a small task, but im sure you could come up with an easy solution.
If you go with a cassette deck that looks like yours (but adds the CD option) you wont run into any mounting problems. The add-on cd player mounts to the stock bracket in the car, so there still wouldnt be any mounting issues... and the add-on cd player just plugs into the back of the cd capable cassette deck.

There shouldnt be any reason in the world why you cant change your speakers too, and not change the look of the car. The speakers mount inside the front door panels... and inside grills in the rear deck... you'll never see them. What model accord do you have? the DX and LX models have 6.5" speakers front and back... and the EX had 5" up front (smaller than a 5 1/4) and 6x9's in the rear.

feel free to email me, sumkidwithacl@aol.com, if you have any more questions or if I did not give enough specifics.