I'm willing to spend 1400 euro on a gaming PC but could not build it myself (would have to go to a shop or have it built on the website, but that's not the problem) I only know a little bit about graphics cards and Processors off.
This neutral report helped me with my choice:
So the price always depends on how good quality you want to play these games. From this point of view it is of course cheaper to have it built by yourself, but you should definitely look for experts. A friend of mine has a recommendation for a gaming PC that should meet your needs. Fortnite can be played with it on high graphics settings and something like GTA 5 works pretty well too. For the price, that's fine in case you want to think twice. In any case, you would have less stress and a good gaming PC straight away.
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