I just bought me a new 221 a couple months ago, so I'm in the same boat with you.
I've killed a pile of foxes with a lot of calibers from 22 LR to 223, and 357 magnum(light loads). I'm in the heavy bullet crowd as far as centerfire rifles go. The light weight bullets blow up a good hide way to often for my tastes. I've shot dozens of foxes with the 22 Hornet, loaded with Sierra 50g SMPs at around 2400-2500 fps, and that combination is fairly fur friendly, although it'll still blow a hole if the range is close, and the angle is wrong.
I'm working towards a 221 load that'll consist of 55g Sierra SPs(a very hard bullet for slower loads), and my target velocity will be around 2500 fps. My 223 loads with these bullets running 2700-2800 fps are pretty fur friendly if I choose my shots carefully, and avoid the shoulders of a fox. I'm figuring from past experience that those bullets at 2500 fps from my 221 should be just the ticket. If not, it'll be back to the 22 Hornet for me.