BruceH,
"Am I correct in assuming that the QS4 and VP100 will be sonically "identical" (or perhaps I should say tonally identical) to the QS8 and VP150 [comparatively] in my smallish room?"
Yes, the timbral match is very close.
Unless you listen at extremely loud levels, I don't think you'd need the VP150 to match the power handling abilities of your Monitor Audio speakers. Speaking of which, British speakers as a group (with some exceptions) generally don't have power handling the equal of, say, the M80ti's, which we routinely run past 800 watts per channel in our chamber.
I don't know what the power handling rating is for the Monitor Audio speakers. The VP100 is 200 watts. Come to think of it, the timbral blend with the center and main speakers is really crucial, so why aren't you considering a Monitor Audio center channel speaker? Or, alternatively, getting two Axiom main speakers that will provide an excellent timbral match to the VP100?
Regards,
