The technical contact at Carver told me that the ZR1000 actually sounds better at least in stock form, but they are virtually identical except for a couple of parts substitutions according to the schematic. I would imagine that the mods would be identical for a 1000 and a 1600.
I believe that either would be good candidates for driving Magnepans. Several folks that have them on this forum drive low-impedance speakers with them.