Been outta the loop...

Need advice for a partial upgrade for my Gaming PC. Was going to grab a GTX1080 used ($300) but definitely need a CPU upgrade because I'd imagine it'd bottleneck a GTX1080. Should I spend more money on my end-of-the-road socket or start fresh on the X370? Is LGA1151 here to stay?

i5 6500 @stock (bios won't allow non-K OC)
ASUS Maximus VIII Ranger (Z170)
R9 290X
2x 8GB DDR4-3000
CPU/GPU waterblocks, 2x 360 rads, D5 Vario

Option 1:
i5 7600k ($180)
GTX1080 ($300)

Option 2:
i3 9100 ($90)
Z370 ($200)
GTX1080 ($300)

Edit: Option 3:
Ryzen ($100)
B450 ($200)
GTX1080 ($300)

Z170 is very dead and not really worth upgrading unless you get an amazing deal. z370 is also likely dead as z490 will probably be a different socket. Intel likes to switch sockets, so I wouldn't count on another generation LGA1151.

x370 is actually AMD.

Since there is so much hype for the new Ryzen stuff, you could probably get a good deal buying something like a Ryzen 5 2600x and compatible motherboard.

As he says and I believe you meant Z370. Unless you plan on grabbing a 8700k later, Ryzen 3rd gen is a way to go, Ryzen 2700 + B450 motherboard with a good enough VRM design (MSI MAX boards, Asus TUF) do the job too, so you could swap for Ryzen 3700X later on.

Thought I had read that somewhere; I appreciate you mentioning that. Not a bad idea on the Ryzen front. Is there a decent $100 Ryzen I could buy and overclock the hell out of?
Yeah I wasn't thinking, meant Z370 haha.

That's was the train of thought I had but was unsure. Ryzen is a great idea and I'll have to look into it.

Is a GTX1080 a decent buy still? Performs better than RTX 2060 & 5700XT for much less

Hopefully some more people jump in with info. I'm not super familiar with AMD stuff. My 3900x is my first AMD since Athlon 64.

I know the 2600 and 2700 and the x variants are really popular and offer way more cores/threads than Intel stuff in the same price ranges. Now that the 3600 and 3700's are out, should be able to grab the last gen stuff for a decent deal.

Also the GTX 1080 is still a great card. I have a 1080 and a 2080... The RTX stuff isn't really a good value for how expensive they are.

The 1080 in my 4790k rig still does 75+FPS pushing 2560x1440 at mostly high settings in all the stuff I play.

You can grab a Ryzen 5 1600 for under $100 pretty easily. Cheapest board I would pair it with is a MSI B450 Tomahawk MAX (make sure you get the MAX variant) so you don't wall yourself off from being able to upgrade to a 12 core 3900X or a 16 core 3950X later though.

GTX 1080 does not perform better than RTX2060 and sure as hell it does not perform better than RX 5700 XT. Not in games.