Upgrading from ios 5.1.1

Hi all - I think I know the answer, but want to confirm...

I have an AT&T iphone 4 (8 gb) that is currently on ios 5.1.1. Of course, the recommended software update is to iOS 7.0.4. However, I'm unable to do this as "the update requires at least 3.7 GB of available storage." -- which I don't have (the "Download and Install" button is grayed out)

The question is, do I have any option to upgrade to iOS 6.x.x? Or am I stuck on 5.1.1 ?

Thanks !
Steve