What JMCgrogan2 sez, except in my experience some power tubes are more linear in tone than others. With those more 'linear' tubes, such as the GL KT88's or SED 6550's I would agree that small tubes can make a greater difference than the two power tubes would make on their own. But with the SED KT88s, which are not so linear, i.e. increased upper bass and extended highs, small tubes matching is essential, as is amp matching. I've used SED KT88s as well as SED 6550's, SED EL34's, and SED 6L6GC's for some years and while I really enjoy the KT88's when they work (as they do now in one of my amps) as often I've not been able to dial them in using other amps, especially those with a more modern design ('neutral' tone, such as ARCs etc). I know nothing about your amps but I didn't care for the KT88's at all in my Cary mono's, but found the 6550's quite acceptable.
If you want a crystal clear toned linear tube, if you can use it, you might find the SED 6L6GC to your liking. It lacks the power of the 6550/KT88 and the mid-range warmth of the EL34, but it has clarity in spades through out the FR.
BTW, what kind of speakers are you using? Do you feel you have maximized your set up opportunities so that they are positioned to sound their best. In a 'dark' sounding room I can imagine that a tubed amp/speaker combo might sound less energized and a SS amp sound better, especially if you speakers are voiced on the warm side of neutral.
If you want a crystal clear toned linear tube, if you can use it, you might find the SED 6L6GC to your liking. It lacks the power of the 6550/KT88 and the mid-range warmth of the EL34, but it has clarity in spades through out the FR.
BTW, what kind of speakers are you using? Do you feel you have maximized your set up opportunities so that they are positioned to sound their best. In a 'dark' sounding room I can imagine that a tubed amp/speaker combo might sound less energized and a SS amp sound better, especially if you speakers are voiced on the warm side of neutral.