ATX case still not needed for a build that doesn't even benefit from a graphics card. Your motherboard is microATX anyway so you could just go with a microATX case.
But, if you really want a massive case with lots of empty space inside, that Phanteks Eclipse is a fine choice. I have a Phanteks Enthoo Pro M myself and it's excellent.
Here's the CPU:
https://www.newegg.com/Product/Prod...3480&cm_re=ryzen_2400g-_-19-113-480-_-Product
The Asrock A320 board you picked requires a BIOS update to version 4.50:
https://www.anandtech.com/show/12426/am4-motherboard-apu-bios-updates
Download here:
https://www.asrock.com/MB/AMD/A320M Pro4/index.asp#BIOS
It won't have that version factory-installed (at least not yet), and you can't update the BIOS without a compatible CPU installed first. Options:
(a) Buy a cheap
A10-9700 that works on all BIOS versions on that board, update BIOS using it, sell it, then install
(b) Buy the motherboard from a vendor that will update the BIOS for you in exchange for a small sum like $10-15
(c) Avoid having to update the BIOS by just sticking with the A10-9700. Upgrade when you feel like the PC needs more oomph.
(d) Wait for new boards to be released that work with Ryzen 2400G out of the box, or wait until current boards come out of the factory with Raven Ridge compatible BIOS versions (no idea when)
(e) Go with Intel i3-8100
Are you sure you need a 2TB hard disk? Doesn't seem necessary for "Youtube TV, music listening, internet, some business applications". The first three are all online use cases so no massive amounts of local storage required, and the space required to install "business applications" is probably somewhere in the range of 1 - 10 gigabytes.
Here's an intel option in ITX form factor:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Core i3-8100 3.6GHz Quad-Core Processor ($118.90 @ OutletPC)
Motherboard: ASRock - Z370M-ITX/ac Mini ITX LGA1151 Motherboard ($126.98 @ Newegg)
Memory: Corsair - Vengeance LPX 8GB (2 x 4GB) DDR4-2400 Memory ($104.99 @ Amazon)
Storage: Crucial - MX500 500GB 2.5" Solid State Drive ($134.88 @ OutletPC)
Case: Silverstone - Sugo SG13B-Q Mini ITX Tower Case ($48.43 @ Amazon)
Power Supply: Corsair - SF 450W 80+ Gold Certified Fully-Modular SFX Power Supply ($89.24 @ OutletPC)
Total: $623.42
+
https://www.newegg.com/Product/Prod...8024&cm_re=sfx_atx-_-9SIA8HV5NU8024-_-Product $7
Can add external USB3.0 storage as needed. Can add a midrange graphics card, upgrade CPU up to a hexacore Intel i7, upgrade memory up to 2x16GB. WLAN is integrated to motherboard.