Argon??? no way unless your welding!! Food Grade Nitro is all you need. Need to experiment with your brew to see which ratio works best for you. Get a dual gauge regulator for the tank. Purchase a quality Stout tap that is made for nitrogen. Not all taps are. 40 lbs at the soda keg is usually sufficient. My kegerator holds two 5 gallon soda kegs and I keep the tank external. They make some that holds 3. Easy to build your own also.