Well I finally have enough time to write this up quick.
I ordered: http://www.alibaba.com/product-detail/2014-NEW-Intel-Celeron-C1037U-aluminum_1694884758.html Their shipping was fast. I got it in three days after they put it in the mail. Unfortunately, for some reason it took them almost a week to get it out the door. Shipping from them was the 'most' reasonable. It is still pricey, IMO.
I added 4GB of RAM to it. I ordered this Atheros card: http://www.amazon.com/gp/product/B00JESLUWQ/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 as some research lent me to believe it would work. It does.
Tip: Order the computer with the cheapest WiFi adapter. Even though the card it comes with is not supported by pfSense it's cheaper than ordering a set of plain antennas. If you don't, then it doesn't come with any antennas and you have to order a set like this: http://www.amazon.com/gp/product/B00MJU6X5U/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
I used an 'old' 40GB SSD I had from my old server. I figured I would never use a 40GB SSD for anything else. It screwed to the bottom of the case.
The case acts as the heatsink. I took it apart to clean and reapply the thermal grease because I didn't trust the glopped on crap that it came with. Also, you will need the newest pfSense 2.2 beta.
There are a ton…metric ton of options in the BIOS. I played around with too many and wound up having to reinstall because I screwed something up and it wouldn't boot into pfSense anymore. I did enable speedstep in the BIOS and then enabled Intel support in pfSense and pfSense recognized it. One thing I wonder about is where I get BIOS updates from?
Here is a link to my build pictures. Google + has royally screwed up my Picasa album and I couldn't get individual pictures linked so I linked the whole thing in one album:
https://plus.google.com/photos/118395195107291110441/albums/6093568438407647809?authkey=COuD-ezPksvppQE
I think for the price this thing is hard to beat with dual Intel NICs and the form factor. With a VPN, 30Mbs down and 5Mbs up, wireless cameras on the WiFi streaming to the LAN, a NAS serving out pr0n to several XBMC and PLEX devices I have CPU usage of less than 5%. It has no moving parts and is completely silent. CPU ran about 50 degrees C and then I enabled SpeedStep and it sits around 47C to 50C.
I'll answer any questions you guys have.