The preamp tubes will have the most significant effect on sonic signature. The power amp 1st stage (the gain stage) will also have a noticeable effect on sonics. Phase inverter/driver will affect sound to a certain extent depending on the design of the amp.
Attributes of the sound such as warmth, dynamics, soundstage depend on the manufacturer of a tube and the tube type. The tubes you asked about are all input tubes, as opposed to the larger output tubes. BTW, we refer to changing the tubes as "rolling tubes."
Brent Jessee has a very good description of how different tubes sound. Click on the tube type that your amp uses.
http://www.audiotubes.com/12ax7.htm