Very good explanation shadorne, and I would agree completely.
Whichever path one chooses, I believe it is best to have the Pre Amp and Amp from the same manufacture and from the same era for optimal pairing and experience the complete sound that each manufacture has to deliver. That being said I went from an Audio Research LS26 and Audio Research VT100MKII, to now a McIntosh C2500 and MC402 ( also an MC275 tube amp ). Many of you would say that was a backwards move but my experience was this:
Both sound very good, the ARC combo is probably "better" in that it is more detailed were as the McIntosh is a bit "softer" and "creamier" if that makes sense. So why did I switch? Because I found that with the ARC I was only able to enjoy a very few pieces of music. Ones that were very well recorded and with the McIntosh everything sounded good. My music preference is mostly old classic Rock recordings of which many are not the full high resolution of some of the best audiophile pieces out there. example old David Bowie was un listenable on the ARC but sounds wonderful on the Mac. But again an Audiogon Jazz Sampler in Hi-Rez was better, more detailed on the ARC. Also with the additional power of the MC402 to my Wilson WP6's, it has dynamic headroom and "punch" for days. I of course would love to hear a Ref level ARC pre/amp but also it would cost more than twice as much.
Also recently added Shunyata Sigma NR power cables to the McIntosh and it takes it to a whole new level of 3D sound stage.
Just my experiences