Thinking of upgrading but not sure what cpu?

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Hi all as the title says I'm thinking in the very near future of upgrading my cpu but i'm not sure what my mobo will take.
I have a Asrock Z170 Pro 4s motherboard and a :-

6th Generation Intel Core i7-6700K
Processor Base Frequency: 4GHz
Overclocked to 4.4GHz
Cache: 8MB SmartCache
I would Ideally like an i9 but don't want to spend any more that £500, would I be better going for an i7 instead?
and would I see much difference in performance?

Thanks,
Danny.

 

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Thanks Orange Nexus for your reply, I'm a bit concerned will my motherboard support a i9, it says it supports socket 1151 and on the processor it says that its compatible with LGA 1151 socket also it says that its compatible with 300-series my mobo is intel Z170 series?

 

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Thanks Finners for that info here is my spec :-

Intel Core i7-6700K 4GHz,
32GB RAM,
3TB HDD,
250GB SSD,
NVIDIA GTX 1080,
Windows 10 Home 64bit

its a few years old now but I got it mainly for my Oculus rift, which I use everyday for gaming.
I do have an LG Flatron 34UM95-P 34" WideScreen Super-Wide LED Monitor running @ 3440 x 1440
What would you advise as an upgrade?

 

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Thanks again Finners, I will look into your suggestions and I'll download MSI Afterburner and see how I get on, Thanks m8.

 

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Sorry Guys, I haven't been on the forums for a week so I never noticed all the replies, thanks everyone, I guess I'll wait for the Ryzen 3000, the reason why I was thinking about upgrading was because I play a lot of sims games ie. acc/ac/rf2/r3e etc in Vr and I don't feel that Im getting near the 90fps everyone keeps talking about, I think I'm getting around the 45fps now I'm certainly not an expert when it comes to getting the best out of my hardware, I kinda just stick the headset on and go so any advice would be greatly received