Yes, you would need Firefox for the Selenium IDE and RC. But after that, you can record the automation of the front end tests. Then you can choose to export those automation results in
Java, Ruby, etc. No manual tests. When you run the automated tests with the RC, you can have the tests be kicked off in IE, Firefox, Chrome, etc. You get to choose what browsers you want your automated tests to be ran on (I usually choose all the browsers).