I am not sure if you can add multiple (e.g., two each) PCI cards on riser boards attached to two adjacent PCI slots.
I went with AMD, so it is not entirely what you are looking for. The specs are:
Motherboard: Foxconn N570SM2AA-8EKRS2H
(which is same as this Newegg item)
(has two Network connections - one for Internet from my home network and the other connected to an 8 port switch for a separate media network)
Video Card : ASUS EN6200LE
CPU : AMD Athlon 64 X2 4000+ 2.1GHz
RAM : 2GB DDR2-800
Harddisk : 500 GB SATA-300
Drives : DVD drive/writer
External Dr: Sony XL1B3
InputDevice: Media center compatible Keyboard/Mouse combination
: Gyro Mouse
: Gyro Remote (not yet connected)
IR Remote : USB-UIRT
: Microsoft Windows XP Remote
OTA TVTuner: ATI HDTV Wonder (unable to get sound - not sure if it is compatible)
: HDHomeRun (not yet installed)
Media Director ======
In my testing setup I am using an old motherboard with minimum configuration as MD.
Motherboard : Intel D815EGEW with built in Video/Network/Audio
CPU : P3 1 GHz
Memory : 256MB SDRAM
(Power consumption of this setup is only about 40W or so.
I will use similar configuration for all my MD where I don't much processing power like music players.
Beefed up MDs are required only to decode HD contents)
I decided on external TV tuner because it won't take up PCI slots or system resources. Not sure if you need much processing power in the core, if you are not using it as MD. As far as I know, MDs uses its own resources to decode HD contents and all that. So that means even if you are going to have core/MD hybrid, still the processing power required won't be too high. I am also very new to LMCE so take my advice with a pinch of salt!