I had a system with a Krell KAV 300i and an Audio Research PH-3 and the Grado Reference. It was a great match. The PH-3 (or PH-3 SE) is a hybrid FET input 6922 output. I am still using the PH-3 and the Grado, but not the Krell as I have moved on to a system with high efficiency speakers.
Don't worry about the impedance. The important thing is that the input impedance of the follower stage be higher than the output impedance of the driver stage. That's pretty much guaranteed with any pair of high end components. You may want to play around with cartidge impedance matching at the phono preamp, but it too is not critical and often requires soldering in a resistor. I've done a couple of experiments but the Grado Reference seems to like the PH-3 the way it comes.
Don't worry about the impedance. The important thing is that the input impedance of the follower stage be higher than the output impedance of the driver stage. That's pretty much guaranteed with any pair of high end components. You may want to play around with cartidge impedance matching at the phono preamp, but it too is not critical and often requires soldering in a resistor. I've done a couple of experiments but the Grado Reference seems to like the PH-3 the way it comes.