I've been buying my hardware from newegg.com for probably 15 years now. I find myself in the market for a case and mobo. I have everything else I need to construct a PC. This would be for an Intel CPU. Where are people buying hardware these days?

I have:
new 500W power supply
i5-7400 CPU
32 GB DDR4 RAM
2 SATA SDD drives
NVIDIA GeForce GTX 1660 SUPER GPU

Newegg

Or Amazon if you don't mind the increased risk of knockoffs and part swaps pre delivery.

I just built one in November. The case is the one part I just went down to my local computer shop and bought off the shelf. It was like $120 for a nice glass panel mid tower with four 120mm fans already installed and plenty of room for a 4080 super and 360mm radiator. Good layout, easy to work on and cable management wasn't bad at all. I haven't installed the two optional side 120mm fans yet, but I've had no temp problems running overclocked i9-14900K and pushing the 4080S to it's limits in VR in MSFS and DCS.

Cheaper on Amazon and good reviews:
Okinos Mirage 6

Live near a Microcenter? I'd try there first. They have a lot of cases on display so you'd get a good idea on what your getting and they also usually have good MB/CPU combo specials.

eBay will be your best bet for a motherboard for a 7th gen intel CPU.

ASUS Prime Z270-A
GIGABYTE GA-H110M-A

Case doesn't really matter. You can get a Corsair 4000D from Best Buy for like $100.

Corsair 4000D Airflow

Or there's cheaper options out there

LIAN LI LANCOOL 207

For a case I usually buy from Amazon or NewEgg. Sometimes one has stock and the other doesn't, or better price, etc.