Multi subnets on one nic , moving to one subnet per nic

[brcisna]

Hello All,

pfSense-1.2.3-RELEASE
First want to say what a reliable platform pfSense has made for our school router/firewall scenario! Thanks to all of the pfSense devs for what they do!

1. Current lan setup after several changes over the last two years in our main school building.
Subnets:
server rack & secretaries    =  172.28.8.0/24  # all static Ip's
high school                          =  172.28.13.0/24
grade school                        = 172.28.11.0/24
admins  & teachers            =  172.28.15.0/24
The building is setup with gigE backbone via gigE uplinks ' on 24 port switches down the hallways", with 10/100 going into classrooms.
As current setup with the pfSense router in place all four subnets are static routed down to the .8 network switch in the server rack through pfSense.
Each subnet has a separate running linux terminal server( which provides dhcp for thin clients as well) are providing dhcp to fat clients/workstations. This is just the way things have came about over network changes over years. Ip phones added ,etc.

2. Possible change to try and clean things up and leverage more pfSense nics;
I have gotten an WatchGuard Firebox with 6 nics. I am trying to picture if my theory of the following would be more efficient?
I would like to control all dhcp through pfSense box rather than multiple linux running servers.
If I were to simply run one nic per switch from pfSense box nic(s)and eliminate the Linux servers of dhcp duties.
Ultimately the routing comes down to the .8 network of which the actual servers are.
I would still have to have the static route entries in the pfSense box as they are set now.
Caveat: One problem is the x series WF only has 10/100 nics so my gigabit throughput is not going to happen even though we are in a gigE switched enviornment.
The current pfSense box is an cast off 1u server that has only (3) 10/100 nics so it is not doing gigE itself to LAN even.

Bottom Line:
Current
pfSense box 3 nics  2- WAN ports  1 - LAN port plugged into .8 switch

REDO:
pfSense box  6 nics  2 - Wan (s)    1- Lan .15 switch  1 - Lan .13 switch 1- Lan .11 switch 1- Lan .8 switch

I can not really get my head around if this "more nics" would allow the possibility of better throughput overall? ( not taking into account the gigE snafoo on this setup)
Would 'more hardware links' equate to more possible throughput?
I am not getting any "the internet seems slow at x hour of the day",but just trying to utilize what we will have for next school year.
Sorry for long post.

Thank You,
Barry