1 server, 2 nics = service to both?

I have a Dual G5 tower running OS X 10.5 server. A cable modem provides its internet connection.

The cable internet service I use is awful, dropping out on a regular basis. 😠 (It manages to fail in such a way that the server can still reach outside addresses, but it's impossible to connect to the server from the internet.)

My only other option for home broadband in my area is 3Mbps DSL. 😟 My question: if I add a 2nd ethernet card to the G5, is there a way to configure the server to offer all services to BOTH interfaces - providing 2 different routes of access? 😕