They make products--more precisely, they <i>market</i> products--specifically for stuffing cabinets. I know Parts Express has a version which I believe they call Acousti-stuff or some such term. They (naturally) claim that it's miles better than ordinary polyester. Maybe, maybe not. For all I know, it's the same material. Just be aware that it's out there.
I use ordinary polyester fiberfill here at Chez Bear.
Now, I have seen several tests that indicate that long-fiber wool is superior to polyester. It's somewhat more common in Britain than it is here. Due to the weight, some people rig ways to keep it from settling over time.
Grey