So the speakers are ***84dB 1 watt/1 meter***! If a speaker that was only 90 dB (which is easy to find) the amp he has now would make the same sound pressure. The thing is, the bigger you make a tube amp, the harder it becomes to make an output transformer that has bandwidth. Because big tube amps are expected to make bass, often its the highs that suffer but often the bass suffers a bit too. The only exception to this rule is if an OTL is used; then its possible to scale the amp to any power without loss of bandwidth.
But a 200 watt OTL on this speaker is impractical- and that would be only to maintain the bandwidth he has already. So it makes more sense to change out the speaker for something more efficient than it does to change out the amp- the latter is nearly a Sisyphean task. Even with 200 watts this speaker isn't going to be able to make satisfying sound pressures in most rooms if you want to play anywhere near realistic volume levels.
But you don't have to lose any resolution (in fact many think that you gain resolution) with higher efficiency speakers. In my example of my first post on this thread, I showed that an amp of 1.7 watt could keep up with his BAT amplifier if that amp was on a set of ZU Audio loudspeakers. This means that a 7 watt amplifier could keep up with a 200 watt ARC in the same circumstances.
The bottom line here is its very obvious that the speaker needs to be replaced if tubes are going to be used.