Although I left said job, I still have some knowledge about market - at this very moment AMD is dominating intel both by price and performance, exceptionally when we talk about CSGO performance. Would rather go for Ryzen 5 3600 like someone higher sugested or Ryzen 7 3700X - should run everything in future 10 years unless we, as humanity, will find a way to push miniaturization. RTX 2070 should be optimal. Unless you are youtuber - I would suggest to invest more in ~500GB SSD and less into HDD (1TB is more than enough). 650W is optimal as well. Also - one thing I learned from experience - fancy cases are often loud as fuck and their fans are shit, you may want to reconsider this.
Last thing - you have to know that warrant is universal for PC building shops and separate parts - there is really no difference if you build it itself or pay big money for someone else.