Your preamp output impedance is very typical. The input impedance of you amp is on the low side of normal. Typical for a SS amp is 50K and for a tube amp 100K even though some like yours and I believe the Nelson Pass amps are a little lower.
A general rule of thumb says the goal is an input impedance at least 100 times higher than the output. This, of course, is open for debate. Yours is closer to 50, but that should not be a problem as you attest to with your observation that it sounds great.
There are several issues. At the pre-power interface your goal is to transfer voltage from the pre to the power. As the power input impedance drops it draws more current from the pre. Some pre amps don't like this and become non-linear. You also drop more voltage across the output impedance of the pre amp so less is available to the power amp. You then have to turn the volume knob up higher. Depending on the overall gain of the amplification, this could be a problem if you run out of voltage before you get it as loud as you want.
On the other hand, a higher input impedance makes it easier for noise to makes it's way into the power amp. So you want a high input impedance to make it easy on the pre amp and low impedance to minimize noise. You can't have both so a compromise is made.
There is also a camp that advocates matched impedances including the interconnects and another that uses a current transfer design rather than a voltage transfer like your more typical design.
A general rule of thumb says the goal is an input impedance at least 100 times higher than the output. This, of course, is open for debate. Yours is closer to 50, but that should not be a problem as you attest to with your observation that it sounds great.
There are several issues. At the pre-power interface your goal is to transfer voltage from the pre to the power. As the power input impedance drops it draws more current from the pre. Some pre amps don't like this and become non-linear. You also drop more voltage across the output impedance of the pre amp so less is available to the power amp. You then have to turn the volume knob up higher. Depending on the overall gain of the amplification, this could be a problem if you run out of voltage before you get it as loud as you want.
On the other hand, a higher input impedance makes it easier for noise to makes it's way into the power amp. So you want a high input impedance to make it easy on the pre amp and low impedance to minimize noise. You can't have both so a compromise is made.
There is also a camp that advocates matched impedances including the interconnects and another that uses a current transfer design rather than a voltage transfer like your more typical design.