PIX-515 Firewall

Recently purchased a Cisco PIX-515 firewall. I am told that I have 3 configuration options available.

#1 – Move all nodes to 1 public subnet.

#2 – Continue to use both public subnets.

#3 – Use private IP addresses on all nodes and use network address translator in the PIX to allow access to external network.

Option #2 is my choice as it requires the least work on my part. However, I am told that I will need an additional router because multiple IP addresses cannot be bound to the inside PIX interface to route between the two subnets.

What kind of router (number of interfaces, etc.) would I need for this. There are so many choices to sort through.