Earlier quoted context omitted.
+1 on that. There are a number of online build-to-order shops here in the UK which offer a truly vast range of component combinations. Better still, the order process automatically checks for compatibility with, for example, your choice of motherboard. Once you have the configuration you want, you just pay up and it arrives professionally assembled ready to rock. I don't think I'll ever by an off-the-shelf machine ag…
I found the premium on these was quite high, although even just buying all the components from a single place added a fair amount to my recent build. Compatibility, price checking and searching are all available with PcPartPicker (UK site: https://uk.pcpartpicker.com/ ) which saved me an astonishing amount of time. The hour or two building the machine were worth the few hundred it saved me, but everyone has different…
Often times in those cases you also get great service because a) if you build PCs for a living you're a computer geek and it's fun to build an insane PC and b) they often use their biggest systems as advertisement. At least, that's what I've seen.
+cable management is like black magic to me. If I were to take the money saved as payment for me to get it as nice as those places get it, I'd be below minimum wage.