He makes a few models of poweramps that are at or below 33kohm input impedance, this then will have a ? for a passive to drive at 100% perfect impedance match.
But to counter that Nelson Pass does make his First Watt B1 preamp which is buffered passive preamp, that is just a passive pre with a unity gain simple two transistor active buffer, which then can drive these or other poweramps that are at or below 33kohm input impedance.
And yes he does make proper preamps that have gain and are $$$$ but he is a business man, and needs to make money.
In the OP's case he can drive his PSA dac direct into his Cary amps and have the prefect match with no preamp in the way.
Cheers George