Well I am with you on the pfsense choice - I can say nothing bad about it that is for sure.. Been running it for a few years. m0n0wall would be a good choice as well if your looking for something with a smaller footprint and less bells and whistles. I have to say that m0n0wall ipv6 works click click, while I have had some issues with pfsense and ipv6 native - works great with a tunnel like hurricane.
Pushing 100mbit doesn't take much - fitting it into a 1u rack as far as cases, etc is prob going to be where some of the cost is.
Comes down to your budget - sky is the limit you could spend whatever you want.. If you looking to keep cost low you can go different routes that may or may not fit into your 1u rack.. Have a home rack would be killer, and each room with 2 runs at cat 6 sounds fantastic.. Sweet setup it sounds like!
As to the consumer level comment - dude it doesn't take much to surpass that.. The soho stuff is quite often just crap - hardware wise some of it is not bad, but the firmware they put on them is just pathetic.. The problem is they try to make it for the masses that don't have clue one so they leave out all the good stuff. I would love to see a soho native firmware that has say vlan support on the lan ports - sure many of them provide guest wireless, but how come I can not do vlan tagging on the switch ports? What about ssh access? Snmp support? Openvpn server? Captive portal? etc. etc.. Firewall with actual logs that show me what was blocked other than just gibberish that you were attacked but not tell me the actual port, etc..
Now not sure if my pfsense vm could push 100mbit -- but I would have to think it could since I see 900mbit to my other nas vm.. And its running on a n40l with other vms running and only given it 512MB of ram.. I would have to do some rewire to test what it could push wan to lan doing nat with firewall, etc. So don't think you need some highend MB with GB of ram, etc. Look to good ethernet - your best place to ask about good hardware for a pfsense setup in 1u might be the pfsense forums.
If your looking to running pfsense on other type appliances boxes - there is lots of that going on on the pfsense forums, I just don't have access to other appliances to play with or would be active in that section as well.
Whatever you go with - let us know how it turns out!!! And if you need any help with pfsense just PM me, or see you on the pfsense boards I am very active over there as well.