Selecting volume pot for specific output impedance

I have a tube preamplifier with an output impedance of 1.6K and I'm trying to select the correct volume potentiometer for the power amplifier to match to this. Am I correct that the general rule is 10:1, which would put the volume pot around 16k? Assuming this is the case, would 20k pot be a good choice, or would it be better to be up around 50k to be safe?
 
There probably isn't a right or wrong here, at least without more info.

If your preamp with the 1.6k output impedance can maintain its performance (distortion and LF roll off in particular) into say a 22k (20k) pot then go for something like that. If it can't then you need to go higher.

Also consider the input impedance of whatever you are feeding the pot into and any capacitive loading such as HF/RF filtering on the input as that can roll of HF response if the pot is to high.

I suspect ultimately something like a 47k (50k) or even 100k is probably more suited tbh. It all depends on how well the preamp handles a load.