Hello Grannyring, you are correct. The higher the output impedance of any preamp, the shorter the IC should be.
However that does not explain bass response, but some of that depends on your speakers too, and whether you listen to recordings where the issues might show up. This is an area where audiophiles will say things like "this preamp has more impact than than that one" even when both preamps cut off at the same frequency. IOW, its in a realm of 'in comparison to what?"
What we are talking about here is issues with phase response, which behave to the ear more as a coloration than a frequency response issue, although when the phase is right you do get more impact.
However that does not explain bass response, but some of that depends on your speakers too, and whether you listen to recordings where the issues might show up. This is an area where audiophiles will say things like "this preamp has more impact than than that one" even when both preamps cut off at the same frequency. IOW, its in a realm of 'in comparison to what?"
What we are talking about here is issues with phase response, which behave to the ear more as a coloration than a frequency response issue, although when the phase is right you do get more impact.