I've got a fresh new 10600K install (about 3 weeks now), and I'm getting 5ghz on 3 cores, 4.9 on 4-5, and 4.8 on 6. With that I'm only running temps in the low to mid 30s idle, up to about mid 60s under load. That's with the Noctua 12S with an aggressive fan curve, which is fine by me since I can't hear it even at 100%. Given those thermals, I figure I could easily go to 5ghz all core, but I'm new to the whole OC game and am being conservative until I learn more about what I'm doing. I'm basically letting my MB's AI and the XMP profile control my OC.
Now, maybe the silicon lottery gods smiled upon me and I got a chip that can handle OC better than average, I can't really speak to that. I guess I also got lucky just getting one at a reasonable price from a reputable retailer in a timely manner, as it seems like as soon as they get a shipment in, it's gone, and you have to pay scalper prices or wait it out. I got it for $289.
Since you're going to need a new MB anyway to go Intel, I would strongly recommend against going 9th gen anything, as you would have zero upgrade path without ANOTHER new MB. As far as the i7 or i9 10th gen, I didn't see any point in paying 2x or more for the CPU given the small performance increases they hypothetically come with. The conventional wisdom is that 11th gen when it comes will be supported by the LGA1200, and given the delay in 7nm, I suspect that's even more true now than ever.
Anyway, lots of things to consider, I was where you are a month or so ago, and initially thought I'd go AMD, but the 10600K changed my mind. Good luck!
KevyKevTPA