>>One thing that occurs to me is that the quality of the reconstructed
sound has more to do with the interpolator rather than the sample
rate.<<

i have a feeling that because the synth has non-bandlimited oscillators, that the sample rate itself is pretty important, or more importantly, the aliasing effect it has is very important.  i think that that reason why 28khz is sounding 'better' than 44.1 is because of more high frequencies folding back over and thickening the sound up in the low end.

i could be totally wrong, but that's what it sounds like.

44.1khz is 'thin and wimpy', but at 28khz it's a thicker, fuller sound.