Lots of options out there if you're willing to reload.

For a non-reloader: .22Win mag or .22 Hornet.

The 17cal rimfires are fine and dandy, but they haven't proven anything to me that would make me put them over the .22WMR.

For 25-50yrds, any of the rimfires would be fine.

I'd be going with (and do use myself) a .22WMR when Fox are the target of the day.