Ok, with Theo's help. Here is what we are looking at:

Operation cool running, small footprint DVD/Music library PC

1. Micro ATX case w/300w power
2.GIGABYTE GA-EG45M-UD2H LGA 775 Intel G45 HDMI Micro ATX Intel Motherboard
3.Intel Pentium E5200 Wolfdale 2.5GHz 2MB L2 Cache LGA 775 65W Dual-Core Processor

The intel G45 was chosen for its cool running chipset (100f degrees cooler than the same board with the Nvidia 9400 on it).

That figure looks WAY overestimated; how did you arrive at that? (ambient internal system temperature != operating temp of the GPU)

The specs I've been looking at are definitely about lower temperatures & lower-voltage efficiency, but still...

The GeForce 9400/9300 chipset is in fact NOT a 'set' but just a 'chip' - it uses a single chip design to integrate all traditional north brdige, south bridge and GPU features into a single die. This gives the NVIDIA product some advantages: easier motherboard design, cheaper to manufacture (in theory), easier notebook design. It also creates one bigger issue though: a concentrated power dissipation and heat area. In my testing the chipset heatsinks on these motherboards got VERY hot - over 200F in one case compared to the Intel G45 north bridge heatsink that never went over 100F. While this doesn't actually cause any problems out of the gate there is the potential for issues down the road for overclocking, stability and burnt fingertips.

http://www.pcper.com/article.php?aid=627

Hmm... well, if you opt not to use the onboard video, in favor of the nVidia 8600 GT we discussed, that will probably take care of the heat concentration issue which the article mentions. In that case you'd use a DVI cable rather than HDMI. Also, this way you'd have more raw 3D rendering horsepower for your flight-sim aspirations.

Alternately, if you prefer to stick with the onboard video, you could use an HDMI cable, and we'd have the room to replace the factory heatsinks with beefier versions (since the PCI-E card wouldn't physically obstruct either one).

UPDATE: um, I realize we're actually talking about using the mainboard which DOESN'T use the hotter nVidia chipset (chip), but we'll check the running temps of the onboard components regardless. If they do run hot, we can work on that.

personally xbox 1 lols, http://www.xbox-linux.org/wiki/Xebian just splice the cables for a xbox and wire them to keyboard/mouse or usb ports, and put in a bigger harddrive. but you dont get to do much building.