Tried the GPX 5000 on high mineral CA ground, with the stock DD ,very quiet and stable, no gold yet. I found plenty of small caliber bullets previously detected with my TDI. Depth on some bullets was 22in, this in ground that stacked one inch of that black stuff on my magnet pick. For you motor car fans I would compare the TDI as a stock car and the GPX as Indy. The cost percentage is about the same too.