ovrphil:
I never subbed better speakers in the RCA Mark console, though I did a test listen with some ADS speakers I had that would have fit in the cabinet, and it sounded great. In fact I'm saving those small ADS jobs for just that purpose should the right console come along. The 6BQ5 (EL-84) output tube is one of the sweetest, the open frame trannies are fairly decent sized (one shorthand way to judge quality of an amplifier) and the RCA's amp/preamp/tuner section is quite decent overall imho. Due to significant damage the cabinet wasn't good enough to pass the "spouse filter", however, so it went away and the electronics were spared.
112561/Alan: you're correct, the Fisher consoles rarely had speakers that lived up to the excellence of the electronics, even the President we had had less than top notch drivers and crossovers, Jensen derived iirc, as the bean counters dictated cost savings there, and in general the really serious listeners didn't buy consoles but instead sought out components that they could tailor to their own specific tastes and idea of good sound so while you didn't get the pretty cabinet you got more flexibility in placement, and the same money went to where it really counted.
The RCA Mark had all it's speakers in one untuned, unbaffeled and unlined compartment, making for a less than thrilling sound, but it was more than adequate for the bulk of casual listeners who mostly used them for enjoying Liberace, Johhny Mathis or Mantovani (all of whom I love, btw) while dining.