Well, I can see you are defiantly pulling out all the stops here... xD
Well, here is what I can say about it already:
With your GPUs, I didn't know know that NZXT G10 thingy even existed! I'm thinking about adding to my build! Thing is, if you're going to get that, you're going to have to get 3 more water coolers, and I highly doubt you've got the room. And even if you do, what's the point getting such a 780ti with 3 cooling fans if you're just going to take them off again to add this on? I don't quite think you understand what it is... In short, it is a cooling piece for the GPU. What you would do is take off the original cooler (yours being the case with the three fans) and attach that, and then you would get a water cooler, such as the H100i or the H55 and attach it to that and you would have water cooling for your GPU. But the thing is, you're getting 3 780ti's and that means you would need 3 more water cooling blocks. Believe me, you're not going to need it with that cooler. And a question, how come you're getting 3 GPUs? I've got 2 and I can run any game at ultra with everything enabled and still get around 120FPS minimum. But it's your build, I just personally think you're not going to need it.
For your CPU and CPU cooler... How come you're going for the 4960x? It is so more expensive when you're only getting a 0.2GHz boost in normal clock speed and 0.1GHz in boost. Believe me, save you're self some money and get the 4930k, unless you're willing to wait for the 5930k. But who knows how much that is going to be... And by looking how much you're going all out on this, I would advise you waiting for the 5930k. For you're cooling, I would save the money from swapping the 4960x to the 4930k and buy a H105 with 4 Noctua NF-F12s or 4 Corsair SP120s because they will be much MUCH more quieter then the once that come stock and will be much better at doing what they do. You don't have to get 4 though, that is only if you can fit it.
Also, how come you're only going for 16GB RAM? I thought you would of gone for 32 at least. Anyway, if that is what you want... I would advise trying to find some 2400MHz ram that is 4GB sticks and get either 4 or 8 of them. I know it sounds stupid but it would be better than 2x8GB.
Also, for your storage. I am wondering why you're getting a 250GB, a 500GB and a 4TB. Just a little confusing. Personally, I would swap you your Samsung 840 EVO's for some Kingston HyperX 3K 240GB SSDs. If you really want a 250GB and a 500GB, you could always have the 240GB and the 480GB. My reason behind this is because the Kingston have a 15MB/s read boost but a 10MB/s write loss. You're only really be using the write speed for when you're downloading and installing software. The read boost will give a fair bit of difference between boot up times, game load times and all things like that. And for the HDD, it's a good choice. I like it.
Your BlueRay drive is fine too.
Is switching 3-way SLI to 2 * Titan black worth it?
Not a chance. The Titan Black is literately the exact same as the 780ti, just with a very small clock boost and 6GB of GDDR RAM instead of 3GB. The GRAM will make no difference in the games, or anything in that matter. So, no... If you're really set on having 3-way SLI with the 780ti, sick what that.
For your headset, there are MANY choices which you could choose. This is the one I would recommend for you. Sony Pulse Wireless Headset (As you're a bass lover, I couldn't recommend these enough.) There is also this one. This may not be as bassy as you would like, but for gaming, you honestly cannot get better, I promise you. Audio-Technica ATH-AD700X Audiophile Open-Air Headphones. The reason you should get these is because when you're playing a game, you want to know here the bad buys are, and this headset gives the best positional audio compared to any other headset on the market. And for the question if you should buy a separate headset for gaming, my answer is a yes. Beats are good (although overpriced) for music, not for gaming.
For your keyboard, there are many many better looking keyboards out there which are actually just better in general. I've got 2 and I would highly recommend looking at them. 1. Cyborg V7 2. Logitech G19s
The GamePad, I don't see the point in getting. You're just not going to use it, believe me.
Speakers, great choice but I don't know too much about speakers so I cannot make a great judgement.
For your monitors, I can't help there either... I've got 3 BenQ XL2720Z which are fucking amazing, but only 1080p. For your case, you could always get the same one as mine... The InWin GRone. Cant say much about it other than it is awesome!
That link you posted is in short, a PCI SSD. It looks beast and I could recommend getting it. It's just like adding another, faster SSD into your machine.
The soundcard is badass. Oh, so very badass indeed. So, no need for a secondary sound card, and the Wi-Fi that comes with it is also amazing, but it is completely up to you if you want to buy a secondary Wi-Fi card.
There you go, you wanted some advise and there it is. Took me about 1 hour to type it all and do the research behind it, but it's worth it. Always glad to help.