Here is the case I used in my HTPC:
Newegg.com - COOLER MASTER Elite 360 RC-360-KKR1 Black Plastic (front bezel), SECC (case body) ATX Mid Tower Computer Case Thermal Master 350w Power Supply
COOLER MASTER Elite 360 RC-360-KKR1 Black Plastic (front bezel), SECC (case body) ATX Mid Tower Computer Case Thermal Master 350w Power Supply
Great case, well built, fits ATX and mATX boards. Its nice because it comes with rubber feet so you can lay it on its side and stick on a TV stand instead of having a tower off to the side. The only issue I ran into was the video card. The PSU is mounted in the front, with the video card directly behind it. I originally planned on putting a GeForce 9600 GSO in it but the power connectors came off the back instead of the side which made it too long. So I ended up having to put in a shorter, newer GeForce GTS 250 which had power connectors coming off the side.
If your only using the PC for movies and music you really don't need a whole lot of system power. Go with an AMD chip and save the money. You find cheaper boards, and cheaper CPU's. I recently built a system with this chip and board:
AMD Athlon II X4 640 Propus 3.0GHz 4 x 512KB L2 Cache Socket AM3 95W Quad-Core Desktop Processor ADX640WFGMBOX $102.99
GIGABYTE GA-MA785GM-US2H AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard $79.99
$25 off in a combo. It plays Starcraft 2 at max on a 9600GSO with 4GB's of DDR3 at 1280x1024 (although you would probably need a more powerful video card at a higher res). However I do agree on the Blu-ray, you can always wait and swap it out late.