2 ISPs and 1 LAN: Bridging? Or what?

I’m a part-time Net Admin who now has TWO ISPs (with fixed IPs) coming into my shop. My boss wants them both on my LAN providing in/out access. I have a SBS2003 PC available and all the NICs I need. The SBS2003 PC will also be providing Exchange services for my LAN and internet clients. What is the best way to implement all of this?