Finally decided to go ahead and get PFSense going for my router/firewall - the snow gave me free time to set it all up.
Hardware:
NCS Gemini CK3-A325 minitower PC
2.2ghz Intel Core 2 Duo E4500
Asus P5GZ-MX motherboard with Marvell Gigabit LAN
Intel Pro1000 PT Single Port PCI-E NIC
1gb DDR2-667 RAM (1 stick)
SeaSonic 350w 80 Plus PSU
Chenbro Case
So, I got the hardware cheap from government surplus ($5) + the HDD from eBay ($10). Turns out the P5GZ-MX motherboard has some design flaws. Component quality is fine - Japanese caps, nice layout. The problem is in the PCI-E implementation - the x16 slot is actually an x4 slot and you must disable internal video to use it. You also must use a GPU in that slot...so no Intel dual port PCI-E NIC's can be used.
Of course you still have the option of the 1 onboard Marvell PCI-E NIC + a Intel PT1000 in the 1x slot, this is supported.
There is always the 2 remaining plain PCI slots, but I am unsure as to the throughput capacity here. I ordered a 2 port Intel PCI GigE NIC off of ebay from Hong Kong so we will see...
So, aside from the PCI-e limitation the hardware is really nice. The case is super solid and the fans are whisper quiet. It runs cool (duh, 2.2ghz Core 2 Duo is not exactly a heat generator).
As for PFSense the experience has been pretty good. Its a little iffy with Comcast IPv6 and it takes a dance of resetting the modem and PFSense box to get an address picked up. You also have to disabled Bogon network blocking as the current version of PFSense (2.2) has a bug with the order of default rules which blocks Comcast's IPv6 DHCP system if you block Bogon networks on the WAN....
Performance is excellent and has reduced my ping time very slightly when compared with the Asus RT-N66U. The addition of a real IPS system and the ability to block wide blocks of IP addresses based on location is a huge plus.
The 2.2ghz Core 2 Duo is barely stressed with a 105mbps connection, even with Snort running. Average load is 3%!