Take a close looks at the connectors in the links Randy posted, that is the most visible difference. Also look at the inputs on your EP500 and you can see the RCA inputs you are currently using and the input for the balanced connection.
The main advantage of balanced cables you can't see. Inside the cable the wires are designed to cancel noise that commonly occurs the longer the run.
It doesn't read like you have balanced connections on your other equipment so don't worry about it just get a RCA cable with really good shielding. Some guys use a unbalanced to balanced adaptor on their RCA output jacks and use balanced for the long run. I never have so I can't speak to its effectiveness. You may not have unwanted noise anyway so it could be a non-event and RCA throughout would be fine.
Here is a quick primer.
http://www.ofsoundmind.com/OSM2/tech/equipment/balanced.html
