From the SP17 manual:
OUTPUT IMPEDANCE: 210 ohms Single Ended main; 20K ohms minimum load and 1000 pF maximum capacitance. Outputs (3): 2 main, 1 record (Single Ended RCA connectors). Record output 60K ohms minimum load and 100pf maximum capacitance.
It seems your amps may not mate well with the SP17. I don't know the extent of the implications in the real world.
The SP17 is still a fantastic preamp.