Depends on your needs. Do you want it in a very small box? One with no extra noise from cooling fans? Can you use a bigger box with some noise from cooling fans? Will you do more than watch blu-ray disks? Gaming?
Almost all medium to high-end boards built since 2008 can run blu ray or HD on Windows Media Center, Vista, or Windows 7. You'll need an HD graphics solution, either built-in to the board, or through a discrete video card, and a blu-ray capable Optical Disk Drive.
I'll use my pre-existing nvidia geforce 8600GT (a few years old, but still works fine), samsung bluray player, superflower 600w psu, WD 250gb hard drive, two tv tuners (to allow recording and viewing simultaneously), 4gb ddr 2 RAM and antec sonata III case (quiet computing case, supports regular ATX motherboards) and Win 7 home premium.
I won't be doing any gaming on this computer, just media for a Samsung 52" plasma (I think), so I'd like pretty high quality video.
You'll need a larger HDD to record HD. The hauppauge 2250 is HD with ATSC/NTSC/QAM tuners. It has two tuners built in (along with hardware decoders, saving some CPU utilization), and allows recording on one channel, while watching another channel. Do you already have a CPU that you can use?
Now you're getting somewhere. Looks like you need 1 PCIe x16 (full length) for the 8600GT. Modern TV tuner cards are PCIe (usually short slots), you want 2, so you'll need 2 of those. Do you need any regular PCI slots? A floppy drive? Any IDE/PATA drives?
so there's no compatibility issues between normal cases an micro ATX mobos?
As I recall the Sonata cases have the stand-offs for both ATX and microATX.
I did forget to find some RAM selections; I was tired.
.........I've had a change of heart and decided to go with the AMD Athlon II x4 640....
That's OK, it's your money. I'm not that familiar with AMD systems, although I've thought about building one. Still, read the motherboard manual while you're waiting for delivery. I hope it POSTS on your first attempt.