Like all K2000/K2500s, the K2600 is always in a 16-Channel Multi Mode.

This means that Kurzweils are always responding to all 16 MIDI Channels at the same time. But they can not respond to 32 MIDI Channels.
32 MIDI Channels can only exist when there are two separate sets of MIDI In/Out jacks (MIDI A/MIDI B, like on the E-MU E-Series samplers).
The confusion that you're having comes from the heavily-advertised feature in which the K2000/K2500/K2600 Sequencer can have up to 32 Tracks. This is because you can use Song Arranger to make a Song play another Song at the same time. (16 Tracks x 2 Songs = 32 Tracks)

The tricky part of this is that you can make 16 of the Tracks go only to Internal sounds and 16 of the Tracks go externally via MIDI. This is cool, but it is not the same thing as being able to play 32 Channels of MIDI that is coming in on the Kurzweil.

Bottom Line: 32 Tracks - 16 MIDI Channels   (Not 32 MIDI Channels)