core i3 6100 vs i5 6400

Definitely the i3. Even if they used the same GPU the i3 would be better in many games since not all games can fully utilize 4 cores and the i3 would be better due to the higher clock rate. i5-6400 is just there to say "don't buy me, look at i5-6500".

i3 6100 + GTX 960 is the way to go. That i3 is quite capable.

If it's the non ti version, yeah the GTX 960 is at least 2x faster.

I3 2@3.7ghz vs I5 @3.3ghz... in gaming the difference is not much 5-7fps. The only time you will see a difference is in AAA titles that demand a great deal from the CPU that would favor the I5 slightly. Without overclocking these two Chips are pretty close.

:lol::lol::lol::lol::lol:

:lol: I couldn't agree more.

I just don't understand why Intel makes a bunch of CPUs that are so close in price to each other...

AMD use to do the same thing with the Phenom series.. every 6 months they would do a .1mhz bump and sell it for $20 more.

Well first off, my inclination is to recommend the i5-based build, so that you don't get scammed by an unscrupulous seller. GTX 960s only come in 2GB or 4GB flavors, so you cannot buy an 8GB model.

Secondly, not sure why you would even consider the 750 (especially a non-Ti version), when for about the same price (about $10-20 USD more) you can get a GTX 950 (more shaders, more texture mappers, more renderers; slightly faster clock/memory speeds; much better pixel/texture fill rates; higher memory bandwidth; supports both DX12 and Vulkan APIs; much higher GFLOPS, despite having technically the same GM206 processor; & the 950 supports 2-way SLI). Not to mention the 750 is 3 tiers down from the 960, while the 950 is only a single tier down (http://www.tomshardware.com/reviews/gpu-hierarchy,4388.html).

Thirdly, your GPU choice is going to depend on a number of factors, but the first one is going to be your resolution. Planning on gaming at 1440p or higher? You're going to be sorely disappointed in the 960's performance, as you'll be wanting something more like the GTX 980 or an R9 390/390X. Only gaming at 720p (or similar, such as 1680x1050)? Even the GTX 950 is more than sufficient for those resolutions, as it's the "playable" option for 1080p gaming. So, if you're going to play at 1080p, either the 950 or 960 will work, but even the 960 will struggle to hit Ultra settings, especially on newer games; you want that performance, you'll need to buy a 970 or better.

That brings up the next consideration: what games you will be playing. And that's not just what you have now, but what you plan on buying in the near future (i.e. within the next 3-6 months minimum). For games already released, you should check benchmarks to see how much of an effect the CPU choice has on the game performance. Take, for example, Battlefield 4 & Star Wars Battlefront. BF4 doesn't seem to be very CPU-limited (http://www.techspot.com/review/734-battlefield-4-benchmarks/page6.html); as long as you have at least 4 cores, even an Athlon X4 chip will perform about as well as a Haswell i7. In contrast, SW:Battlefront seems to be much more affected by the CPU choice (http://www.techspot.com/review/1096-star-wars-battlefront-benchmarks/page3.html), as the Skylake i3 is not only outperformed by AMD's FX-8350 but also by a Sandy Bridge i5. Note that you can also look at benchmarks for GPU performance as well. For example, in SW:Battlefront, the 960 has an 8FPS advantage over the 950 at 1080p resolutions, but even the 960 struggles to hit 60 FPS at Ultra.

For upcoming games it's harder to judge, but you can usually get some good inferences from the developers; for example, the upcoming DOOM game may "only" require a Sandy Bridge CPU from Intel & recommend an Ivy Bridge CPU, but it's a quad-core Sandy Bridge (i5-2500K), & they're recommending a quad-core/HyperThreaded i7. The AMD recommendations are also both quad-core, so I would strongly suspect that a dual-core/HT CPU -- even a Skylake model -- is going to have some performance issues with it.

Obviously, some games will mirror performance for 1 or more of these examples, but the more info you have the better informed the decision will be. For example, if all but 1 of your games show no difference in performance between a Skylake i3 & a Skylake i5, then the i3 ends up being a good CPU choice; on the other hand, if the majority of the games show significant performance improvements with the i5 over the i3, then you shouldn't be surprised at the lower performance.

But this all brings you to the final point: money. First off, realize that whichever build you're looking at buying, you're talking about more than just a CPU & GPU. You're talking about a new motherboard -- & probably new RAM, since the major point of Skylake is that you get DDR4 compatibility -- which means you have to look at your overall build budget. But you also have to consider your existing machine. If you're budget is really, really tight, then consider whether you even need to get a Skylake build. As I pointed out, new game releases are still able to function with pre-Haswell Intel chips, so if you have a Haswell (or even an Ivy Bridge) build, you might be better off just buying a new GPU for your existing build. Heck, even if you have an FX-based AMD build, they may not be "top of the line" compared to Intel builds, but they'll still provide decent enough performance that a new GPU can extend their lifespan. For the cost of either the i3/960 or i5/750 to 950 build, you could easily get a GTX 970 (for 1080p) or even an R9 390/390X (for 1440p). Or, if you're willing to wait another month or 2, you could get a Polaris 10/11 or GTX 1070/1080 for the same prices. But if your budget is large enough, & you're looking to replace an older Phenom-based build or a Sandy Lake build -- or even an old Core 2 build -- then consider what you need for your board as well as the CPU & GPU. For example, since you're not asking about "K" chips, I'm assuming you won't be overclocking, so you probably won't need a Z170 board, & might be able to save enough to justify an i5/960 build.