You said, "...less competent than we are." Who are you as compared to Best Buy if you do not mind me asking?
By we, I'm referring to you, me, and others who know our way around hardware and software. I've not assembled too many new PCs(just 5), but I have gone inside them many times - my own more than anything, as I can't keep my hands out of its guts for more than a few months.
I don't think that highly of myself - I am bloody software stupid. Beyond DDU - gpu driver update, motherboard support site for driver updates, malware scan, and reinstalling Windows, I'm not going to be of much help beyond that.
If only I was actually there with the above PC. It's easier when you're actually there with the patient.
The experience with Best Buy is a mixed bag.
There can be associates in one store that know their way around stuff, providing customers with some of their best experiences ever, and ones in other stores that are not so knowledgeable that miss things like, melted cpu cooler sticker causing overheats, loose connectors and other devices... some believe hot tube-cold tube is normal AIO operation! I'd say I'd fall in the middle.
Then there's management - it's not equal in all stores either. Some don't allow their technicians to do much more beyond virus removal and simple upgrades/hardware replacement. More than that, and it goes to the service center($$$).
Some can replace motherboards in desktops, but not laptops - if the customer brings another board, they may do it.
I suppose they do have the obligation of refusing service if it wasn't purchased there.
OH. Maybe I should've replied by PM..?