You are running into a limitation of sample transposition on the K2000. The K2000 can play back samples up to 96kHZ. As you transpose a sample up the keyboard, its playback rate increases - each octave doubles the playback rate. So if a sample was originally sampled at 48kHZ, you will get one octave of upwards transposition. If you play any notes above that, the sample "pins" and will not play any higher. Of course, the lower the initial sample rate is, the farther it will transpose upwards.
This is not usually much of an issue, since most samples simply do not sound good transposed up that much. As a result, you don't normally run into this that often when importing foreign format samples. However, the earlier Ensoniq samplers simply did not have very much memory, and as a result, they tended to use fewer samples in a file and stretch them farther, particularly in the upper range.
The only thing you can do to get a further upwards transposition is to go into the Sample Editor in the Kurzweil and use the Resample DSP function to convert the sample to a lower initial sample rate. Keep in mind however, that in doing this you will lose fidelity, since the highest frequency that can be accurately played back will be 1/2 of the sample rate. So lowering the sample rate, lowers the highest frequency you will hear in the sample.
This issue is less noticeable for K2500 and K2600 owners, because these instruments have a "sample skipping" feature which enables the instrument to double its upwards transposition limit. Still for EPS files with very few roots, you may still encounter this problem.