Hey Dan,
When it comes to headphone amps, I never can have enough variety of tubes. Even though a given tube set sounds best with one particular headphone, it certainly doesn't mean that it's a universal fit. And unlike speakers, switching headphones is a time honored tradition (and way cheaper too).
So, I take the same tact as CB.
Helpful Hint; if you lay them on their side and stack them with the ends out, you can get quite a few against an 8x22 foot wall.