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A 1080 hands down if they are the same price, especially if it is a MSI 1080 DUKE with its tri-fan cooler. Sure a 1070 Ti can be OCed to match or even slightly outperform a stock 1080, but a 1080 with a great cooling shroud like the MSI DUKE will be able to maintain a higher sustained boost clock with GPU boost and thus outperform a OCed 1070 Ti easily. You can also OC the 1080 even further if you wish. I am 1070 Ti owner myself, which I bought 3 months ago. Back then the 1070 Ti were very close to MSRP (~$470 USD) while the cheapest 1080 I could find was ~$560, so it made sense for me to get the 1070 Ti over the 1080. But now since a 1080 can be found for under $500, no reason to choose the 1070 Ti anymore.

1) I wouldn't feel comfortable with a 500W PSU, since just the card and the CPU's TDP alone sucks up ~300Ws. I wouldn't feel comfortable if the constant PSU wattage usage is above 70% (so above 350W for your case). They say 650W since the 2080 is a high-end card, so they are also taking account for the extra wattage that may come from other parts in a high-end system (i.e. heavily OCed CPU, watercooling, etc.) Since you don't have any of that, I think you would be fine with a good quality 550W PSU. 500W imo is pushing it though. But we are talking about an unreleased card. Wait until tomorrow for the embargo to lift for detailed reviews. 2) Open up your case with a ruler and measure how a 280mm object will fit in. 3) No compatibility issues as far as I know.

@trevor_leong Next-gen cards are being announced in August according to numerous sources: https://www.ultragamerz.com/nvidias-geforce-gtx-1180-to-be-unveiled-next-month/ https://wccftech.com/nvidia-geforce-11-series-graphics-cards-price-fall/ Unless your current GPU is broken and you absolutely need a replacement ASAP, I would wait as the 11 series is right around the corner now.

Just one 1080 Ti will be fine for 1440p @ 144Hz on most games. Having two in SLI would be overkill imo.

That's fine. With that card though you'll most likely be gaming at 720p (or 1080p on older or less demanding titles). Just don't pay more then $50 for it.

@masterRACE The best bang for the buck for $150 would likely be a used 970 on eBay, but since it is an Optiplex, I doubt its PSU can handle it as Nvidia recommends at least a 500W PSU for a 970. With that in mind, I would go for a GPU that doesn't require additional 6pin/8pin connectors. The most powerful GPU around the $150 mark would thus be a 1050 Ti (slightly over $150 actually, more like $170 atm).

@Unknown_Gamer I don't think you need to upgrade your entire platform. The i5 4690K is still a very good CPU for your tasks and you have 16GBs of RAM already paired with it. Like others said above, if you go for an 8th gen Intel CPU, you also have to get a new mobo and RAM (and RAM prices are crazy rn). I would just ditch your H81 and buy a Z97 mobo. Z97s have USB 3.0 and some even have NVMe support. You can still use your current CPU and RAM with it. Idk why you even had an H81 mobo paired with an i5 4690K; the H81 is mainly for entry level, non-OCable Haswell chips. And no, your CPU isn't bottlenecking your GPU unless you're playing at 1080p @ 240 FPS or around that realm.

You really shouldn't be building a rig in 2018 with less than 8GB of RAM.

You're absolutely right.

You had the 4790K for 4 years and you have yet to overclock it? That CPU was made for OCing. Throw a dual-tower air cooler or a closed loop water cooler on it ASAP like the Scythe FUMA or Corsair H100i. You'll easily get 4.5GHz with a moderate voltage increase. Anyways, I think you are overestimating how taxing 1440p could be. There's no practical reason to dish out money for a 1080 Ti because of two reasons: 1) A 980 Ti is equivalent to the 1070 in performance, which is more than enough for 1440p @ 60fps on many AAA titles on high settings. 2) The next-gen 11/20 series GPUs are right around the corner. Why buy a 1080 Ti when you can just buy a 11/2080 in a few months? Rumors say the 11/2080 will also perform better than the 1080 Ti (https://www.rockpapershotgun.com/2018/06/26/nvidia-turing-ampere-graphics-cards-release-date-price-specs/)

It's normal for blower style cards to have higher temperatures. However, you really should consider getting at least one intake and one outtake fan for your case. That will help not just your GPU, but your CPU as well.

You technically could, but why would you? Just use your 760 as is, driving both monitors while gaming on one. If you add the 750 you're just gonna use up more power. You can't SLI the 760 and 750 together so gaming wise it will have no impact.

@LOST TALE 1) If you're planning to use your GPU for many years, go with AMD's RX 580. AMD tends to support older cards far better than Nvidia does. A prime example is the GTX 780 vs R9 290x from 2013. Back when they were released they were neck and neck, with the 780 outperforming the 290x in some cases. Nowadays the 290x is far faster. 2) Future games will require more and more VRAM, so it would be wise to get a card that has more than 3GB even at 1080p, especially if you plan to use it for many years like you are planning to. The GTX 680 was released with 2GB of VRAM, which was considered plenty in 2012. 6 years later, many titles can use more than 2GB even at 1080p.

5GHz is pretty common for an 8700K. If you can keep it stable under a decently extended stress test, go for it. I still would upgrade to a dual-tower though.

You can do a moderate OC with the EVO. Some people really underrate the EVO's capability. There's a reason why it's been the budget cooler king. That said, if you're using a high end CPU, why pair it with a budget cooler? I would pair it with a dual-tower air cooler at least, like this one: https://www.amazon.com/Scythe-FUMA-Rev-B-Cooler-SCFM-1100/dp/B075FX95F2 For $46.99 and its performance, it's an amazing deal.