the size for your civic is 6.5" all around. pioneer decks are good. don't go with aiwa. their decks are cheap. the buttons and volume knobs feels like thin plastics. here are some of the decks that are MP3 compatible:
Blaupunkt MP3000
Blaupunkt San Jose
Panasonic MXE CQ-DFX572U
Panasonic CQ-DP171U
JVC Digifine2.1 KD-SH-99
Jensen MP5010K
Jensen MP 3510
Pioneer DEH-P7400MP
Rockford Fosgate RFX9000