"The other reason to have the bulk of the network L3 switched on the switch is for pfSense upgrades. An upgrade shouldn't take down my ability to stream that webcam video internally, or my ability to stream music or video internally."
While I agree with this for sure, what happens when you want to upgrade your switch firmware? ;) what is being used for internal dns? While you might not have an issue while your streaming a movie or music and you reboot pfsense.
When do you do your pfsense upgrades? I do them after hours or before household hours because I am up early.. Or sometimes whenever.. Reboot of pfsense never takes more than a couple of minutes, etc. If someone was watching a movie I wouldn't do the update then ;)
"The reason I want to segment all this stuff is security."
Completely and utterly agree with you 100% I just do not see doing it at the switch, which clearly while it has some basic ACL functionality does not have the ease of creating the exact firewall rules and logging of hits on these rules like your switch is going to have.
As to how large companies do it - sure they have core L3 switches, I have supported many a large company.. They rarely firewall between their segments, even though they should!! Most often I see a large core switch, say a nexus 7k but there are no ACLs between segments. Sure they will have their services that are open to the public internet behind a firewall and isolated from their core network..
I really don't see that as any sort of reason to do a downstream in your home setup.. If your pfsense box can not handle the wire speed you need between segments, prob better to get a faster pfsense box ;) heheeh It will make your life much easier that is for sure. I have toyed with putting my sg300 in L3 mode and doing a downtream setup.. This would for sure give me way faster speeds between my segments. But the thing is I have my segments isolated for security. The ports I do have open between segments like printing, access to my plex. Pfsense can more than handle the speed needed.
More than happy to help you work out the details of such a setup, I just don't see the actual value in doing it is all ;)