DFX depth? Yea, if you tweak it just right for a very specific spot and all the planets line up properly. By the time you "think* you've got the DFX configured properly with all it's numerous settings at a site you'll look around and find it's night time and all your friends have left with the goodies.
The Minelabs have far less settings that need to be tweaked in order to get it's depth to the very extremes. Never was impressed with the depth I saw the DFX get in the field, and the Spectra to me is just a spruced up DFX. The only thing the DFX impressed me with is it's ability to pull shallow silver out of heavy trash, but then again that was before I had a chance to work that spot with my QXT or now a Sovereign.
Having owned several Explorers I'll tip the hat to the limited time I've had on my Sovereign GT so far. It has got me an indian and a v-nickle that were deeper than I've ever dug with any machine, and this was in a spot I had gridded both directions with the Explorer previously and thought I had cleaned everything out. I was very surprised at how loud and good the two targets hit on my GT.
As I dug deeper I kept thinking "This has to be a large piece of trash" but then digging a little deeper out pops the indian. When I started to dig the nickle I also almost gave up but I'm glad I didn't on that one as well. They were loud with a perfect ID and deeper than I've ever dug those types of coins on any machine. Deeper than even any silver I've dug with the Explorer. I've had very little time on the GT thus far so I'm looking forward to seeing just how deep it's going to pop silver as well.
I've heard some say they didn't think the Etrac was any deeper for them in their soil than the GT. Even if it is let's remember the Etrac comes with an 11" coil while the GT has a 10". Throw on something in the 12" or so size range and I bet the GT will get deeper than the stock coil on the Etrac. If in the future I don't think the GT is doing as well for my style of hunting I'll sell it and pick up an Etrac, but so far I haven't seen anything that would make me think that.
If you're looking for max depth in just about any kind of ground conditions then the top three Minelabs are going to be where it's at, and the large selection of larger coils for them will get you even deeper if you feel the need to. That Fisher does sound interesting and I've heard enough people praise it to be interested. I may try one in the future but from what I've read it's still hooked on iron like Fishers always were, and once ground conditions get rough the depth will suffer more than a Minelab. I always felt Fishers were about ten years behind the competition in audio and discrimination. The CZ line used to be the standard to compare other deep machines to but I always felt they got that extra depth by having such a primative discrimination circuit. Almost like they were running in all metal past a certain depth. Didn't much care for the audio on them either, but I'm willing to see just how far they've come with this newer model.