come in some multi-octave sample format which is not obvious.

If you mean Sound Font format, you may expect it to be supported in some 3.x version of DigiBooster. Also a good source of sounds may be just sampling a keyboard instrument. "Reusing" samples from modules usually gives no good results, as most of samples are of low quality and low sampling rate. I recommend at least 44.1 kHz sampling rate for samples.