Drrsutliff's post raises a question. It is logical to assume you are referring to the Power tubes as these usually wear out first. Are you referring to power tubes or the 12AX and 12AU's? Personally I select power tubes first and then fine tube the amp/speaker combo by selecting appropriate matching tubes.
FWIW I use SED EL34's recommended by Drrsutliff and I use EI 12AX7E's and JJ 12AU7's. For me it is the best combo for a warm yet fairly clean sound. A nice compromise using new production or with the EI's recent production. If I wanted to brighten it up a bit I'd try Tesla E34L's (now out of production) or their successors the JJ E34L's. Caveat - they may not be as rugged as the SED's. If you want something more linear with less mid-range warmth typical of EL34's but with better bass and highs you could always consider SED 6L6GC's. Depending on what I'm using for sources I've like these as well as the EL34's.
Hope that helps a bit.
FWIW I use SED EL34's recommended by Drrsutliff and I use EI 12AX7E's and JJ 12AU7's. For me it is the best combo for a warm yet fairly clean sound. A nice compromise using new production or with the EI's recent production. If I wanted to brighten it up a bit I'd try Tesla E34L's (now out of production) or their successors the JJ E34L's. Caveat - they may not be as rugged as the SED's. If you want something more linear with less mid-range warmth typical of EL34's but with better bass and highs you could always consider SED 6L6GC's. Depending on what I'm using for sources I've like these as well as the EL34's.
Hope that helps a bit.