Sorry got off track on yer question, It would not hurt to add a coil, will it make huge differences, it might and it might not. The crazy thing about metal detecting is so much depends on so much that what works for me here in Northern Utah, may "not" work on a beach in California. This is why I have and still use my old Tracker IV. It works in places other high dollar detectors don't, and other detectors I own work better in places then the tracker IV. I will quote what a very well respected person in our hobby once told me. "No one detector does everything well, that's why so many beeper fans have multiple machines." New coils never hurt, its a cheap alternative, but you don't need (4) 11-12" DD coils of different makes, unless your writing a review. My best advice, if you don't have a DD coil, get one. Why? Cuz you don't have one, and or you have never used one. It might make the difference you need might not, but at least you can now pass along the information you have learned. And that hundred bucks is really not that big a ding if your saving for the high end machine that's $800 plus dollars. I will tell you I have hunted next to a G2 and a T2 got the same depth with my F2, different readings on targets tho. This could have been the ground, the day, my luck, anything. I will also tell you that you have to like what you are using. I had a At Pro, and I just could not warm up to it, nothing personal, nothing against the unit, just the bell sounds the interface, just didn't work for me. I've also had Whites XT, and couldn't warm up to how it balanced and swung, but my friend luvs it. I have been happy with my coil purchases, again they make the machine a different machine, but then there totally different antennas from what was on it. Also DD is not always deeper, concentrics are deeper in some ground but only around the center.