Oh, you are not putting together boxes you found in the attic, you are buying new?
So you heard it's better to have separate amps?
OK, as usual poster like yourself don't disclose the exact nature of your query and we are guessing and try to give you answers that may or may not applicable to you.
IF YOU ARE BUYING NEW...... There are 2 schools of thoughts: (1)One box multi-channel Receiver, this is the most convenient, cost effective and perfectly fine for most homes, or (2)SEPARATE Components, like what I have, a Single Pre-amplifer, this box is the control center, the master switch, then this Pre-amp feeds external power amplifier(s). This second school of thought says, the right tool for the right job. PRO: You get to pick what works best for you and the components can be upgraded individually. CON: Be prepare to pay 3x-5x.
Read the last paragraph carefully, if this is just an intellectual exercise for you.
Buying an AVR and adding external amps is non-standard and unnecessarily complicated, but I commend on your creativity. Buying a Pre-amp + External Power Amp(s) is more standard and will potentially afford you better fidelity as long as budget not a concern.