See the HTPC $1000 build thread at
HTPC $1000 build
Specifically, see jdrom17's post:
End Quote.
I would agree with this. Add in a Blue-Ray player and the software, and you are almost there.
I would start with the HDMI on the motherboard and see how well it works with the 50" TV. You may find it adequate, but then it may have issues like the display doesn't fill the whole screen area, the colours or the frequency is off, or the audio is not going through the HDMI cable.
If you're not happy with the motherboard's HDMI, you may want to add in a very cheap ATI HD4350 (silent or regular one). The (ASUS) ATI 4350 allows you to very nicely control and tune the display, and it also has audio (through the HDMI).