I have a CTX 3030 and have used it quite a bit in heavy nails with the 6in coil but it would not be my first choice out of the detectors I own if hitting a site like you mention for the first time. I would probably opt for the Deus with the 9in x35 coil or VGG with super six, possibly even the Multi Kruzer with 7in concentric. Out of the two you are talking about though I would opt for the CTX, handles iron much better etc.
VGG = Vista Gold Gain?
Yes, I am also on the AKA forum. I have a Sorex pro (non A gain) and it is probably my deepest machine but it sure is a pain in the @ss to set up for specific sites. But once it is dialed in it is deadly deep. I have consistently dug coins at well over a foot Deep.
As far as the E Trac, the noise cancel will only help pick the best channel without outside interference so the ground composition really does not come into play here.
I never had much more luck running TTF in any iron infested spots but to be truthful I have not done much of that style hunting with the E Trac.
Hmm oke.. I only have problems with setting it up in heavy iron if im not using the 6 inch coil. Else I use all settings the same except gain. While GB-ing I reduce gain, get GB, higher gain and go or do manual GB checking and little tweaking and go! Just takes me 2 minutes in almost every field. When I just had standard sorex I just lowered gain to 2/3 get straight GB line and put gain on 5 again and your good to go. Worked as smooth as glass over here. And yea... its deep! But in heavy iron, even with 6 inch coil, its a sucka big time...