Dave, you cannot make general statements like that. Ref 3 and CD-7/8 sound very different to each other, in terms of overall balance - and both are tube based, and both use 6H30 tube.
There is a general consensus that the Ref 3 is a much better preamp than both Ref 2 and Ref 2 mk II, although I can understand that some ppl, in some systems may actually prefer the Ref 2 over Ref 3 for its specific "flavor".
There is a general consensus that the Ref 3 is a much better preamp than both Ref 2 and Ref 2 mk II, although I can understand that some ppl, in some systems may actually prefer the Ref 2 over Ref 3 for its specific "flavor".