One reason to not go with one of the Sanders amps in some circumstances is that while their unbalanced input impedance is 100K, which would be fine with virtually any preamp, their balanced input impedance is only 1K. Many preamps, including most tube-based preamps, cannot drive 1K with good results. And some preamps will sound best when their balanced outputs are used.
Regards,
-- Al
Regards,
-- Al