I was unclear there, sorry been distracted with setting up whole home audio. CPU and MB are kinda picked together... Let me clarify a bit:
Alright so there's different sized chassis and MB's, like footprint wise. First you gotta decide if ya want a baby PC [ITX or MiniATX - which is like the size of console game systems], a standard sized chassis [ATX], or a monster gamer rig with extra PCI slots/onboard SSD, etc.
For comparison here's some pics of my old build; On the top I have a standard ATX MB inside a modified Home Theater PC chassis (this chassis is sized specifically to fit with stereo rack components.]
In the middle I have an ITX [console size MB] inside a second HTPC chassis.
On the bottom is my A/V receiver:
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ITX MB in HTPC chassis (the silver boxes on the left are a CD drive and HDD's and above it is a full size PSU and a couple SSDs) - they make chassis that snug fit these little guys [so adorbs!] I've even seen chassis that can VESA mount on the back of a monitor:
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Typical ATX MB in the same size (though heavily modified) HTPC case as above - you can use this standard size MB in mini-towers, thin or compact towers, mid-towers, and full-size towers:
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And the rig I'm [not really] working on and using right now is a standard ATX MB inside a monster chassis that would fit even the largest MATX board lol:
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It's kind of a game of narrowing down yer choices Tetris style. Like, once you have the MB size THEN you figure out what kinda gear you'll be running. Like if I need a MB that can run quad GPUs without 1x'ing them, or if I want two M.2 drives, or if I'm building a graphics editing rig and I need 128GB of DDR4-3k... Ultimately my MB, both size and capability, is gonna dictate my CPU options quite a bit.
So while the CPU is the real heart of the rig's performance no doubt, you gotta figure out some basic MB stuff first. Once you have a MB that meets your specific needs, then you know what kinda memory you need. After that you pick out a compatible CPU and cooler. Then PCI gear like dedicated GPU's. Then find a chassis that fits your board, GPU, and cooling solution. Then figure out a compatible and strong enough PSU (like some ITX and m-ITX MBs, and some chassis, are built for smaller power supplies like SilverStone's SFX series, or an external PSU brick like you'd find on a gaming console.) Then you can get into your drives. And finally your perfs - keyboard, mouse/trackball/touchpad, mics, webcams, blah blah blah.
Anyway, so AMD's are all I use, but to be fair that's because I'm gaming. Intel's are nice and I don't have anything against em.
Something to think about speaking of my little ITX which is a GPU/CPU combo so I don't have an external GPU and thus can get a "weaker" PSU.
The AMD Ryzen processor series has decent built in graphics. The https://www.amazon.com/AMD-Ryzen-Pr...eywords=amd+itx+cpu+gpu&qid=1582231638&sr=8-8
is a pretty nice chip and there's ITX (tiny size) MB's that they fit in.
You also might consider a pre-built mini-pc - https://www.amazon.com/s?k=mini+pc&ref=nb_sb_noss_2
I'd order the most important bits to put money into a little different, mine goes CPU, PSU, MB, GPU, Cooling, HDD, Memory.