Dual Connections

Hi there, I have been doing some reading but I am unable to get the answer to my questions.

I have two internet connections at home as follows,

1) Cable Connection > Wireless Router > Three PC's - This controls all the general access web mail ftp etc

2) ADSL 2 Connection > Server - This machine just downloads and serves a few files nothing more

I would like to integrate the two connections the browsing PC's can access the Servers file locally.

I do not want to change the way the server connects to the internet and the way the three PC's connect to the internet as I just want to be able to access each one locally.

How I would I go about this?

I am thinking to network cards maybe in the Server or a load balancer?

Any help appreciated.