I have an MXT with the 5.3 Eclipse, 9.5 eclipse, and a 5" excellerator (round). In my test garden, at 2, 4, 6, 7, 8, 9, 10, 11, and 12", all three coils will allert the quarter, dime, nickel, copper cent, and zinc cent (not to mention the liftabs and bottle caps) in ALL metal mode or in discriminate with zero or very low discriminate setting. The CZ20 will do the same thing. In fact the CZ20 will not eliminate a silver or clad coin up to 12" at full discriminate. NOW, you need to plant your own test garden and see for yourself. The MXT will not accurately VDI meter your targets deeper than 6", unless it's maybe a silver coin or object. It will send a false, varying VDI at 7", but no VDI at all at 8" and below. So you'll have to dig anything at greater than 6", for sure. the deeper the coin, the less accurate the VDI, if, indeed, you even Have a VDI at depths of 7" or below. Soil conditions could lessen even those depths.
Finally, if you want a good 5" coil for the MXT, contact Dixie and get one of their Excellerators. You won't be disappointed. They accurately pinpoint, and like I said, they will give a signal at 12" (better in discriminate, with lowest settings, but on super max gain of 3, they'll reach the coins in relic mode, too. HH....