I really don't see any difference in depth over the D2 coil, I got the 13" DD coil when it came out as well trying to get more depth. It gets as deep as the D2 but not any deeper but it does have advantages as it hits better on those deep coins on edge and covers more ground per swing, so its a good coil for open area's as it covers more ground and I've found some deep coins on edge that with the D2 didn't sound good enough to dig. You might have to go bigger than those you mention to get deeper than the D2 coil, like the person above said about the 15x17 you would probably get more depth with a coil that big but I would only use that coil after hunting with another and know there's deep coins there and just check to see if there's any deeper you might have missed. I'm thinking if you want more depth over the D2 you might have to go with the 18x15 SEF coil, I don't think I want to swing that coil though. HH