I am considering taking a X-Terra to Eastern Oregon for my long Relic hunt. I will be hunting old Town Site(abandoned)and Homesteds. My question is which machine would be best. Does the 30 get as good depth as the 50? I am not prospecting, so would that eleminate the need for the 70? Or, is the 70 deeper than the 50 in All Metal Mode.I don't want to buy more machine than I need, but I don't want to need more machine than I bought once I get there.....The other machines I am taking are my Modified IDX Pro, and an M-6 Matrix. My brother and I will need one more machine for a backup. Thanks in advance....poorman