Question Help / Advice Please

Aug 22, 2019
Hi all first time posting although lurked and used this sites advice a few times in the past. So a few years ago I had a major incident with a child and a large drink that pretty much destroyed my pc at the time I managed to cobble together a place holder pc, which I have had far too long now the cheap 2gb 960 I managed to get for it is really not cutting it anymore. So the plan was always to start again fresh modern build. Plan was for a new build either at end of this year start of next.
However through a massive stroke of luck, brother and friends all buying new PC's currently I have got my hands or will do in 2 weeks for very little cost the following parts.
This is what my brothers emailed me so hope this is the right information.

CPU Intel (r) Core (TM) i7 - 6700k CPU @ 4.00 GHZ (8mb Cache)
MB Z170 Pro gaming Asus (r) ATX LG1151. USB 3.1 SATA 6 GB's
CPU Cooler is Corsair H55 Hydro series High performance CPU cooler
PSU Corsair 650w CS series (TM) Modular 80 plus (r) Gold ultra quiet

What I'm planning on keeping from my PC
16 GB Corsair Vengence DDR4 3000 MHZ X.M.P ( 2x 8gb)
My Case fans and Hard drives will all be staying.

So I have a few questions if anyone could help.
Will this all work well together or is it not great. Any advice in general will be really helpful.
I had concerns about ram and PSU not being okay.
Last is I have no GPU I'm at two hearts with this as I'm currently not spending much part of me wants to splurge however my tight fisted side wants to budget. I have been looking online was thinking about £300-600 maybe, now the cheaper side of me is leaning towards AMD Radeon RX 5700 XT (looking online about 350 - 400 at moment) or something similar in that price range. Which leads to more questions about GPU will the AMD Radeon work with the above will a similar price card work. If I was to go nearer the top end of budget or over would the above pc be fine for it. Any recommendations on cards will be really helpful as looking online for a couple hours last night really didn't help me or get me any closer to knowing what to do or buy.

Just noticed I didn't think I mentioned it but mainly gaming.