monitor

1680x1050 was probably one of the most popular 16:10 resolutions, but it lost popularity when 1920x1080 screens were introduced at the same price. The picture quality difference between IPS, TN and VA it's massively exaggerated. It's more about the individual panels and screens. The main difference between them is viewing angles, in particular TN has very limited vertical viewing angles with a lot of panels showing a top to bottom gradient, particularly in pinks and purples.

Your plan sounds perfectly reasonable.

GPU.
I think you're getting your titans mixed up there. nVidia have produced two Titan X models, the GeForce GTX Titan X and the nVidia Titan X. The former is a Maxwell chip, a full enabled 980ti and the latter is a Pascal chip that will also likely be used for a 1080ti. Both support DirectX Feature Level 12_1 though, so you may also be confusing them with one of the older Titans.

The Pro Duo has crossfire issues so it's not worth considering unless it's substantially improved. Vega would be the real Titan X competitor which is likely to release at a similar time to a 1080ti some time in the next few months.

Monitor demands are a wider range than GPU performance, so a card that produces equivalent performance to a RX 480 on a Full HD screen simply doesn't exist. A Titan X running a 4K monitor will produce similar frame rates to a RX470 or 1050ti on a Full HD screen. That will be around 60fps average in a lot of games though.

SLI performance compared to a single card varies on a game by game basis, some games don't support it at all.

CPU

AMD's upcoming Ryzen CPUs are going to launch with 6 and 8 core models with supposedly similar per-core performance to Broadwell. We have no idea of pricing yet but you may find that a 6 core model with an better-than-Xeon clock speed is available for £300.

Storage.
You're wasting your money there, an fast NVMe drive won't bring any practical benefits for gaming or most other things that don't have a lot of heavy disk use. I'd be spending £340 on a pair of 750GB MX300s instead of a single 500GB 960 Pro.

Keyboard.
I use one of these which I find is the best of both worlds for using the mouse with the right hand, but unfortunately it's not a layout that a lot of manufacturers offer. The UK layout version I have is no longer available after Strongman went bust.

If I had to replace it right now then I'd definitely get a keyboard with nothing to the right of the return key, or maybe one row at most if it has narrow borders. Seperate number pads are plentiful, although models with the delete/pageup/etc. keys as well are surprisingly rare.

Wired keyboards also mean you don't have to deal with batteries, although I believe they last a few months these days. You'll also get more extensive backlighting options.