The 2600 can play KN2000, KN3000, KN5000, KN6000 KN6500 and KN7000 type files. (All KN's)

The 5000 can play KN2000, KN3000, and KN5000 type files. (5000 and below only)

For me this makes the 2600 a no brainer, especially since it is a newer model, with more modern features.

Larry