Routers: Cisco vs. Linux?

[Michael Hipp]

I'm planning a major upgrade of my SOHO network in the near future. Many 
of the network designs I've been looking at put a Cisco router ahead of 
the Linux firewall on the T-1s.

What advantage does this offer?

Even a smallish (26xx) Cisco router with 2 WAN ports is a pricey affair 
compared to a Linux box. Stated another way, I could have several 
hot/cold spares for my Linux firewall box for the price of a spare for 
the Cisco. And my impression is that Cisco routers aren't inherently any 
more secure than a "hardened" Linux box.

                   Cable Internet
                     fallback
                       |
                       |
  2x T-1 bonded  |  Linux   |         DMZ LAN
================| IPtables |-------+--Apache Server
    (Cisco?)     | Firewall |       +--DNS Server
                    |    |          +--Email Server
                    |NAT |NAT
                    |    |            QUARANTINE LAN
                    |    +------------ Win box
                    |                    (suspect of viruses, etc.)
                    |
                    |                 PRIVATE LAN
                    +---------------+--Win2k App server
                                    +--Linux desktops (x n)
                                    +--Win desktops   (x n)

Any other comments on this design?

What PCI port card would anyone recommend for direct connection of the 
Linux box to the T-1s?

What specs should I plan for the firewall box given that it needs to 
handle up to 3 Mbps of WAN traffic plus a fair amount of LAN traffic?

Thanks,
Michael