Set up a Network for Two Zones or Floors

I need to replace a somehow fried network setup, and need suggestions on how to recreate it, given the described building layout, situation, and the (what should be plenty of) equipment on hand.
Building Layout:
•      Zone 1
•      Zone 2 (with a working cable modem)
A single Cat6 RJ45 cable connects the two zones, as no wireless signal can cross between the two zones easily, due to construction materials (think super bank safe or something…)
Equipment:
•      One (1) NETGEAR FS116 16 Port Fast Ethernet Switch with Auto Uplink (10/100)
•      Two (2) ASUS RT-N12/B Wireless-N Routers, both upgraded to DD-WRT v24 preSP2 [Beta] Build 16785 (mini build)
•      The one (1) aforementioned cable modem
I don’t think I need to (nor want to) buy any more equipment.
Desired Outcome:

A wireless signal must be accessible in each zone (so one DD-WRT unit per zone), and any PC in either zone must be able to find PCs and print to printers in the other zone. Seamless roaming between the two zones (e.g. as one passes immediately from one zone to the other) must be possible without loosing the connection. All PCs need firewalled internet access, and I’m thinking hopefully on a single subnet (mask 255.255.255.0) around 192.167.1.X for simplicity, for both zones of the building. I’d also like as many wired ports to be available as possible in Zone 2 (near the cable modem), as there are more electronics (printers, internet appliances, etc.) in that zone.

The 500-point question:
Including connectivity and DD-WRT mode (e.g. router, gateway, switch, AP, etc.) settings, how would you set up this network to achieve these results?
Best setup provided (that I can accomplish per the description) wins.