Are you factoring in the long term cost delta? A two channel system
using gear likely to hold its value is much easier to put together than
a similar five channel. In fact, using the confirmed fact that each
speaker and amplifier channel of a stereo system must be the equal of
the single amp and speaker of a mono system, which was widely conceded
when JFK was the driving force atop the Monroe Doctrine, each of the
five channels of the five channel system must be wholly equal to the
two of the stereo system to provide comparable quality. Five excellent
speakers are more expensive than two-I don't see any way around it.

Add in the spectre of correct room design for best five channel
presentation vis-a-vis two, and we are talking a daunting prospect.
Nevertheless, some will demand five channels, then seven....so my
advice would be to buy a system of modularity where you merely add on.
This would also seemingly argue in favor of the monoblock amplifier, if
one wants the amplifier separate from the speaker, unless you buy three
stereo amps and leave one channel unused.