The front end valves will probably be fine, so I'd replace the power valves first.
No harm in having a few spares though, and different makes will have slightly different sound, so it's worth buying some different makes and seeing which you prefer.
“Music has always been a matter of energy to me, a question of fuel. Sentimental people call it inspiration, but what they really mean is fuel. I have always needed fuel. I am a serious consumer. On some nights I still believe that a car with the gas needle on empty can run about fifty more miles if you have the right music very loud on the radio”
Hunter S Thompson