I am using a tubed McIntosh MC2300 pre with McIntosh MC 501 solid state monoblocks. They are wonderful matches!
I have a BAT VK-3iX preamp. When I first got it, I used it to drive Sim Audio amp as my main system. I was happy for awhile until I got my 2nd system, a 300B SET amp with more sensitive speakers. I found my 300B SET amp had more bass than my main system!
So I sent my preamp to BAT for power cap and output cap upgrades. The output cap upgrade tripled the amount of capacitance and thus lowered the output impedance at lower frequencies. Sure enough, I had more bass after I got my VK-3iX back from BAT.
Then a friend loaned me an amp with tube input/gain stage, which has a higher input impedance. The bass further increased! That is the amp I am using now: tube gain stage and SS output stage.
IMO, a ratio of 10:1 between the amp-input-impedance and preamp-output-impedance is not enough. I would say 100:1 is about right.