Amp-preamp mismatch?? result higher volume. What is rthe cause??

Several months ago, I changed amps from a BAT VK200  to a P.S. Audio S-300 amp. I also invested in a new interconnect, the Audience "Ono"  which replaced  a basic Harmonic Technology " Truth Link" which is used  now between the preamp and the CD player  The P.S. Audio amp is very dynamic  but also more forward, but not aggressive 

Pre-amp is a Conrad Johnson PV-14SE and which I like very much 9uses two tubes in the output stage.  The current combo of interconnects has sounded louder (and more forward in the midrange) at the same volume setting used before with the BAT amp  To its credit, the P.S, Audio provides better detail and depth in the midrange than former BAT amp  

So, is there an impedance mismatch between the power amp and pre-amp??   Or  is the increase in volume a consequence of a mismatch between the interconnects, either to the amp or the connection between the amp and pre-amp??

Please advise.

Thank you

S.J.