i have paired the following tube amps over the years with the c7, super 5 and mon 40
cj prem 11a
ram modjeski rm10
vac ren 30-30
primaluna dialogue hp prem
linear tube audio zotl40 ref
audio research vt60, vt50, vt100-2, ref 75, ref 110
only in the case of the higher arc tube amps and the lta did i feel the sound quality was to my liking... in most cases i felt the bass to be too muddy, mid bass too plump and slow, and highs need more definition
i found happiness moving to high grade solid state amps, such as class a models from pass, belles, and hegel amps (not class a), along with the agd audions most recently... primare odyssey and naim units were also good, but not as good...
my taste, my system, my experiences and findings, hope that helps