There's a clip calculator there, but essentially you can take the total sq. ft and divide by 5.
Rows of hat channel are spaced every 24" along ceiling. So you look up and see a row every 2 feet.
Lets take a look at just one row of channel. You'd see that there was a clip every 48" along the length of that one row of hat channel.
So not a lot of contact points, and large increase in the flex of that ceiling. Decoupling brings a whole other level of isolation. Nothing more than R19 is needed, from a practical standpoint. Insulation offers a better payback in terms of performance when installed in a decoupled system.
Same for the mass of the drywall. Double 5/8" rock is more effective if mounted on a spring (clips + channel).
The selection of the correct channel is critical. You'll get this locally, but here's an article that emphasizes the importance of proper channel.
http://www.soundproofingcompany.com/library/articles/furring_channel_with_resilient_sound_clips/