just to get off topic a bit further - as for tube mounting, it depends. Big high-heat tubes (845 for example) only can be mounted vertically. It spec's this in the tube manuals - the RCA manual is a good resource if there's any question. Other lower power tubes - sure, sometimes they are mounted horizontally/etc. There can be heat issues doing this though - sometimes dissipation is not as efficient. Preamp tubes - mount however, they dont' generate all that much heat. more heat = less life, when it comes to tubes. (within certain limits of course).
YMMV,
-Ed
YMMV,
-Ed