Not sure about the TA amp. There are some 12AX7 tubes that will provide a change in character. All depends on the circuit of the preamp for the tube position you change. I found the Mesa SPAX7 seems to have a bit of roll off on the top frequencies. It is essentially the same tube a the 12AX7A stock tube.
There are some other variants in the 12AX7 family, short plate like the Mesa tube generally have the least influence from mechanical vibration. Medium plate tubes like the 7025 (generally the Chinese variant has a medium plate) also the Tung Sol, Mullard CV4004, EH12AX7, Svetlana (all from the same company but difference character in tone ) to the long plate Mullard RI 12AX7, as well as the JJ ECC803s. Warmer tubes would be the Mullards or the ECC803s but that all depends on the tuning of the circuit the tube is in.
Believe it or not the Mesa stock tube is dark sounding in one amp (Roadster) or the RA on the clean channel but bright and grinding on the hi/lo as well as balanced and masterful with the TC-50 and JP-2C. Tonal character you will hear from the tube is dependent on the circuit that is using it. In some cases you may not even notice a difference.