I've wondered about making a restrictor plate setup that threads onto a perlick 4xx series faucet. If you want the creamy head, cascading bubbles and somewhat flat beer like a guinness/murphy's/boddintons etc you do need a blended gas at higher pressure and a stout faucet. It's nice to have if you're into those kinds of beers, I just got a second faucet so I can have 2 of the 6 taps be set up that way.
You can kind of fake it with a "creamer" faucet, but it's not quite the same.
Plenty of stouts are served without fancy faucets, though.