Will the I9 9900k be worth it?

I don't think its worth it, that 7700K should handle any game out there without issue.

I would hold onto your 7700k, its still a very capable processor.
Given your cooler, I would look into overclocking and waiting it out for several more years.

Will it perform better? Yes.

Is it worth the price for the amount of improvement you'll see? No.

Generally, the top of the line processor is not the best bang for the buck, in any case.

4C8T is still enough for all current and foreseeable future games unless you are aiming for the absolute highest frame rates possible under all circumstances for the 5-10% of the time where an i7-7700k might not be sufficient to achieve that.

It also depends on your target resolution. If you are gaming @4k then I imagine the different being sub 3-4% in terms of fps with the GPU taking much of the load. In my opinion, with gaming in mind, the only reason you would want to upgrade from a 7700k would be if you had a super high refresh rate 1080p monitor and you just needed those frames to reach your lofty goals.

Only you can truly tell whether it is worth it. Yes it is the very best CPU in the enthusiast sector beating all from the Ryzen's through to Intel's own 8th Gen CPU's including the 8700K. The key difference is finally 8 true cores and 16 threads allowing it to finally beat the Ryzen 2700X in the productivity side which was the Achilles heel for the 8700K.

With your current Power Supply and the 360 AIO, you should be able to get the 9900K to run out of the box at it's boost quiet effectively without really having to change anything, and with MCE on it will run 4.7GHz all core all day long and turbo to 5 GHz on one or two cores so it will provide a boost over your current setup, especially at high refresh rate or 1440p/4k resolution gaming coupled to your 1080ti. Though at 4K the CPU becomes far less of an issue..

The problem is the cost....Let's not beat around the bush, it's expensive at nearly twice the cost of the Ryzen 2700X and a nearly $200 over the 8700K (which is a stellar gaming CPU) and provides performance in the 15 to 20% region depending on a few factors.

Bottom line, if cost is NOT an issue, then it is a great CPU that will give you the best performance across the board no questions asked for quiet some time...

Would I buy it if the cost was not an issue....Hell yes!

Another thing worth considering: according to rumors / leaked results, Zen 2 may be about 13% faster clock-for-clock than Zen+. If true, then Intel won't have much if any performance edge over AMD left next year and with Ryzen 3 being on 7nm, TDPs should be much lower than Intel's 8.5th gen.

turn the fps counter off, enjoy smooth framerate.

that i7 7700k is a very capable cpu

For the games you currently play, what is your CPU vs your GPU usage?

If the CPU is maxing out at 100% but not the GPU, then a CPU upgrade would help. If the GPU is maxing out at 100% and the CPU is not, then upgrading your CPU will improve performance.

The 7700K has been surpassed by the 8700K and now 9700K/9900K, but, as long as streaming is not in the equation, the 4c/8t 7700K still does *quite* well in the 8700K comparisons I've seen, down by a few percent in BF5 comparisons...

BF5 shootout - https://www.youtube.com/watch?v=cAsyo8gIyys&t=478s

(I'd stand pat waiting on the 10nm/7 nm entries next year or so, unless a streamer, and/or, perhaps having too much money burning a hole in my pocket even after getting a 2080Ti and a 144 Hz monitor, etc...)

I think, as King_V says below, if your CPU is maxing out over your GPU then the upgrade will yield results. How much more though is hard to say. It's a lot of money to pay for the CPU and resulting motherboard upgrade and all the time spent assembling the rig again. But, of course, you'll have the best one around at that point (for a brief, glorious time).

I'm just hoping they come out before I fly back to australia in early January so I can buy one in the US if the performance is awesome, probably will be later than that but a man can dream

^This.

Another thing to consider if you are really looking at the i9 9900K is as of now its over priced and most reviewers are having real difficulty recommending the processor based on performance and price. Its a processor that really doesn't have a real place in the marketplace. Intel has billed it as the most powerful gaming processor, but you get nearly the same performance by overclocking a 8700K as most titles don't use more than 6 cores and the only difference between the 8700K and 9900K is number of cores and clock speed. For pure gaming number of cores really isn't an issue (as stated very few games take advantage of more than 6 cores) and clock speed can easily be overcome by simple overclocking. In reality the i7 8700K based on price and performance is the best pure gaming processor available right now.

If your looking at the productivity capabilities of the i9 9900K it also falls short due to its price bracket. While it productivity is impressive, beating out the i7 8700K and even the R7 2700X, it falls a long way from the AMD Threadripper processors in its same price bracket. That is what is important to remember, Intel likes to compare the i9 9900K to the R7 2700X and say they are in the same class, but that really isn't the case when the i9 9900K is priced as high as twice the cost of the R7 2700X. In the ~$600 processor market the i9 9900K wouldn't be competing against the Ryzen R7 2700X, it would be competing against Threadripper 1920X, 1950X, or 2920X. All of the listed Threadripper processors make better workstations for productivity due to higher core count, but are in the same price bracket.

That is why the i9 9900K is just so hard to recommend. It isn't the best option for gaming (the i7 8700K is a better pure gaming processor for your dollar), its not the best workstation at the price bracket when you compare it to Threadripper. And its not the best all around gaming and workstation when you consider the performance of the Ryzen 7 2700X at half the cost. Overall gaming on the i9 9900K is only around 16 - 20% better than the 2700X, and around 16% better for workstation use. which is good until you factor in the 9900K is $580 and the 2700X is $300.

In short, your better off either keeping your existing processor and seeing how much extra performance you can squeeze out of it with overclocking or if you need to upgrade now and need the best pure gaming processor that makes sense go for the i7 8700K.

To be fair to the i9-9900k, you'd need to factor in the platform cost handicap since the cheapest TR4 boards still cost twice as much as no-frills z390 motherboards.

Very ture, however we should also factor in that 7nm Threadripper will more than likely still be able to use the same motherboard. I don't see 10nm Ice Lake using a z390 board so there is no upgrade path with Intel and greater value in the X399 board.

While AMD's platforms may have more forward-compatibility, what is the actual percentage of people who will ever upgrade the CPU on a motherboard? I suspect more than 95% of motherboards get buried with the first CPU that ever landed in their socket. Much of the time, by the time most people want a faster PC, they want an updated motherboard with refreshed IOs too.

I don't know, I guess I'm odd, I had three different processors on my old Sabertooth board. I'm also planning to upgrade to Ryzen 7 7nm on my ROG Strix X470-F. If you buy a quality motherboard you have a better chance of upgrading by just putting a new processor in it, well you have that option with AMD, Intel not so much.

Unless you buy an entry-level CPU, there generally aren't many worthwhile upgrade options within modern sockets' lifespans. Someone who got an AM4 platform with a 1600X only gets a 10-15% boost from upgrading to a 2600X and maybe a 30% improvement with whatever the 7nm 6C12T CPU will be called. Unless there is a massive improvement in how well-threaded mainstream software is, most people with a 1600X or better will have little to no reason to upgrade within AM4's lifespan.

In 2020, we'll probably be hearing about AM5 (or whatever it gets called) to support PCIe 4.0/5.0, native USB 3.2, DDR5, maybe some form of native Thunderbolt, etc.

To be fair, unless AMD delivers on the rumored/ leaked 13% (or maybe greater) IPC gain with 7nm I probably will stick with what I have. If I do upgrade I'll put my current processor in another rig, sell it as used and discount it a bit, it will still sell and it will "justify" buying a new 3700X (or 3800X) when they come out. But if there isn't at least double digit IPC gain I'll be happy with my 2700X till the next gen boards with DDR5 come out.

Boy there's another scary though... DDR5. I wonder what they will be charging for that considering how much DDR4 has gone for.