PSU: 450W would be the safe bet. Look for an Antec, OCZ, FSP, Fortron, and the likes.
CASES: Anything mATX would be fine.
GPU: Nah, you don't need a gpu. Use the onboard IGP ATI Radeon HD 4200 which can handle 1080p in Windows. Linux, not so much due to sucky drivers/media players.
BD/DVD: I think it'd be best to pick up a drive right away cuz otherwise, you're picking up a DVD burner. Might as well do it right now and save the $20. Most slim mATX cases have only 1 5.25" drive bay. Unless you're talking about towers/desktops.