George and Goodmore are right on with the sensitivity as auto is good to learn the Sovereign, [size=medium]but if you want the depth than auto is the way to go[/size]. There are other factors for depth too is how well you know your Sovereign, good headphones and going slow to. The Coinsearch coil is one of the best coils to learn the Sovereign with and the depth is awesome once you know your detector well as I have dug coins over 12 inches deep with that coil in a park, but they were some very weak signal and I had to go real slow too, like maybe less then a foot a second in order for the coil to see them.
One of the things in my opinion is the original Sovereign for me didn't have the depth the others do, but some feel it is and I tried 2 different ones after I learned my Sovereign XS and I was not impressed at all with the 2 I tried, I think my deepest coins was around 4-5 inches.
The Sovereign is a different detector and most will tell you they though they made a mistake at first getting one, but those that learned them will probably tell you they are one of the best detectors if not the best they have ever used and will always have a Sovereign in their line up of detectors.
Good Luck and good hunting.
Rick