Just catching up on the week's posts...
I was faced with the same question about 2 years ago - not really knowing if there is a solution to this problem, or what to call it if it exists... the functionality you are looking for is [these days] called a "pre/pro" - short for "preamp/processor".
This family of devices is essentially a modern AVR ("Audio/Video Receiver") - but
without the amplification being built-in.
Basically, yes, you do need something that is able to decode the various formats of multi-channel material - as well as doing some potentially complex DSP work for you, ranging from simple "tone controls" to extremely sophisticated "room correction" equalization.
Once you have some or all of this in place, then you get to select your amplifiers... these of course come in 2-channel form (for normal Front Left and Front Right), 3-channel (adding a Center), possibly 4-channel just for your overheads in a full "immersive sound" setup, as well as various Rear and Side surround channels.
If you will be, say, using your home theater setup for at least semi-serious music listening also, then you could do something like using a higher-end 2 channel amp (and speakers) for your Fronts, and possibly more "average" amplification for the rest... but this discussion can turn into a "religious" war pretty quickly (opinions diverge).
Good luck!