The use of NOS British* tubes for input and driver/splitter positions, warmed things up considerably, for every customer that asked, back in the day.
Amp's manufacturer didn't matter.
Nor: whether octal or nine pin miniature tubes.
The carbon composition resistors, used widely in older tube amps, gave them a warmer signature. Even SS gear could be warmed up, by swapping those in for cleaner resistors.
*ie: Mullard, Genelex or Brimar
Brent Jessee's site has a wealth of information, as regards the presentation of the valves available in the NOS market.
http://audiotubes.com/
You could warm up your existing system's presentation, by installing British valves in your LTA preamp, whatever your current amp.