QUOTE(Decrepit @ Apr 2 2021, 02:41 PM)

Best, or at least one of the best, PC assembly / parts sites is PCPartPicker.com, imo. Building guides and suggestions. A "System Builder" that canvases numerous sales sits so that your choice for individual parts is not restricted to any one firm, and you can see who offers the best prices. I used it when deciding on my current and previous PC builds. I believe its system builder will catch most if not all 'broad' incompatibilities, but likely won't catch stuff like ordering an after-market CPU cooler that proves a bit too tall to fit the particular case you want. (Assuming you need after-market cooler. You might not. Or you might buy a CPU that comes sans cooler, thus requiring one.)
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PCPartPicker.com (link)
That said, I reiterate that this is an absolutely abominable time to buy a good quality GPU. Prices are inflated beyond credulity. It's entirely possible that Boutique PC Builder companies have an edge here, possibly having insider access to cheaper GPU than we do. But that's pure supposition.
It's less of price and more of availablilty.
Stores that build to order and prebuilt computers have access to parts. They get stock, and use much of it to fill orders for prebuilt PCs vs selling the part solo. That's why there's such long wait lists. They'll get parts and have to use them for the whole systems first.
I haven't been able to yet source a 3000 series GPU as a side result. It's crypto mining. If they'd only somehow make it impractical to use GPUs for crypto mining, the supply chain wouldn't be so dang broken.
The reason I did not suggest PC part picker is because you still have to build it yourself, or did the last time I was on it. It is no longer always cheaper to build your own. Some people just can't. I have difficulty seeing pins with my poor eyesight, so I had Komplett build mine. I picked a barebones system, and told them what I wanted them to put in it. They built it, tested it, sent it to me with all the documentation and software and parts and stuff. And the packaging. Everything was packed neatly into the motherboard box and then into a slightly larger box with the rest of it, including stuff like the antennae for my wireless card.
And then there's the problem of troubleshooting a build that isn't booting, among other things. I've built plenty of PCs in my day, and there's nothing more annoying than finally getting it together, and turning it on.... and no POST.
Fek. Then you gotta figure out why it's not starting properly, and so on and so forth.
Of course, I'd recommend Komplett in a heartbeat, but yall aren't in Scandinavia.
Oh, and hi miro.