I have a 2005 Civic hybrid and an Insight. The stock CD player in my Civic is shaped like |--/ Maybe the older 01-03 CD player would fit, but an 05 won't.

What about getting the 6 cd changer the plugs into the back of the tape player and hides under the seat?

If you get something aftermarket and don't want to cut any wires you can get a Honda plug adapter.