How many power supply devices do I need?

ooooohhhhhhhhh.

Why do you need an external LPS on the amp and AVR?  

The HDPLEX looks interesting with it's variable voltage. But it does not indicate amperes.

I owned a Chord and it really does benefit using a LPS.

I dunno, it seems everything needs a power supply.

thanks for info on chord dac.  

Amps and AVR’s have internal power supplies that are sufficient to drive the component. They could be switch mode (SMPS) or some type of linear. On the back of these components most likely there’s a IEC connection, which you plug your power cable into.

The Chord Dac has a small internal SMPS power supply and is able to accept a larger linear PS thru the plug in the back. Typically a linear PS is less noisy and more robust which can improve SQ.

The Roon also accepts a LPS, but I've never used one. You need to ask other Roon owners.

Unless you have a known problem from the power company, I would just think of Isolation from Equipment (refrig; sump pumps; washing machine, ac; whole house fan ...), and Overload/Spike Protection.

I have two dedicated circuits: isolated ground from the panel. One for pre-amp and amp; other for all the sources. That circuit only powers 2 things at a time, my Remote Line Controller and whatever I am listening to.

Regarding protection, I got a vintage unit with specific features

https://www.usahifi.com/sites/default/files/product/494/manuals/Adcom%20ACE-515%20AC%20Enchancer%20M...

Not a big power conditioner, spike/surge protection with sequenced on/off design.

Over 42 years, 5 different TT, current Quartz DD, AFTER their motors warmed up (especially Thorens TD124), never heard any sound deviation while listening or saw effects in strobes.

Another consideration is location, cord lengths, wires passing near/behind ___?