285/380, maybe 380X?
SSD?

Razer Synapse was being a piece of shit and didn't set the dpi correctly.
The problem was solved by uninstalling it and just using the native dpi as everyone should.

#734
The PSU isn't great, oversized and usually overpriced.
RAM should really be 1600MHz CL9.
Also the mobo is DDR4, the RAM is DDR3. You'll have to change one of them or it won't work at all.
And no GPU.

Budget and prices might help aswell.

#732
low-rated != bad
low-rated = cheap

An HDD rated for 55TB/yr will work perfectly fine if its workload is <55TB/yr. If you tax it with 400TB/yr it won't last long.
UREs are unavoidable the question is what rate can your setup tolerate before the probability of data loss becomes too great.

Noise rules out the Toshiba MD04ACA.
So I'd say ST4000DM000
http://tweakers.net/pricewatch/330154/seagate-desktop-hdd-st4000dm000-4tb.html
If you insist on a 3 year warranty it's either the ST4000DX001 SSHD, surveillance HDD or the
HGST Deskstar NAS
http://tweakers.net/pricewatch/372300/hgst-deskstar-nas-4tb.html

URE E-14 for all of them.

#729
But what if I'm not in the UK?
checkmate.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600 3.3GHz Quad-Core Processor ($325.00 @ PCCaseGear)
Motherboard: Gigabyte GA-B150M-D3H Micro ATX LGA1151 Motherboard ($139.00 @ PCCaseGear)
Memory: Crucial Ballistix Elite 8GB (2 x 4GB) DDR4-2666 Memory ($99.00 @ PCCaseGear)
Storage: Samsung 850 EVO-Series 500GB 2.5" Solid State Drive ($249.00 @ PCCaseGear)
Video Card: Asus GeForce GTX 980 Ti 6GB STRIX Video Card ($1149.00 @ PCCaseGear)
Power Supply: EVGA 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($159.00 @ PCCaseGear)
Total: $2120.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-30 20:41 AEDT+1100

Optional:
M.2 SSD
Mobo with SLI support (PSU should be plenty, sadly there are no good fully modular PSUs with lower wattage at a lower price in AUS)
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600 3.3GHz Quad-Core Processor ($325.00 @ PCCaseGear)
Motherboard: Gigabyte GA-Z170MX-Gaming 5 Micro ATX LGA1151 Motherboard ($269.00 @ PCCaseGear)
Memory: Crucial Ballistix Elite 8GB (2 x 4GB) DDR4-2666 Memory ($99.00 @ PCCaseGear)
Storage: Samsung 950 PRO 512GB M.2-2280 Solid State Drive ($529.00 @ Scorptec)
Video Card: Asus GeForce GTX 980 Ti 6GB STRIX Video Card ($1149.00 @ PCCaseGear)
Power Supply: EVGA 750W 80+ Gold Certified Fully-Modular ATX Power Supply ($159.00 @ PCCaseGear)
Total: $2530.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-10-30 20:40 AEDT+1100

That's pretty old, almost 2 years.
At least try 14.12 if 15.7.1 didn't work. You did try 15.7.1 not 15.7?
Yellowish tint?

#2
Best bang for buck is still the 290. Not within the budget at ~250$ though.
Imho 390 > 290 though.
If you could get a 290X (~390 performance) for 250 it would be absolutely untouchable.
Either way the 970 definitely isn't best bang for buck since it's slower and more expensive than the 390.

#4
I'd recommend the R9 285 or R9 380 (same card).
e.g. http://pcpartpicker.com/part/gigabyte-video-card-gvr9285wf2oc2gd
or http://pcpartpicker.com/part/xfx-video-card-r9380p2255

#10
Mobo can't bottleneck.

#11
New OS -> new drivers
Which driver version are you using atm?

*XL2411Z

You should probably add "lightboost/ULMB yes/no" to that list, it's kind of important.

Just check the CPU and GPU usage. If one of them is constantly at or close to 100% you've found the bottleneck.

EDIT: I might just test it myself if I'm bored.

Clocks are meaningless if it's not the same chip. Especially if it's not even the same architecture.
The original Titan is chilling at 837MHz base clock and I'm pretty sure it's a lot faster than either of those.

You're also forgetting that the 750 Ti reference got a 1020MHz base clock and can boost aswell.
http://www.gamersnexus.net/guides/1592-superclocked-vs-stock-video-card-benchmark

#721
Added.

#722
At least 100$, probably more.

#723
You linked a GPU and no PSU.
I don't think 12GB SSDs exist.
And it's spelled "vengeance".

How much time and effort do you think I should invest in helping you if you can't even be bothered to check what you wrote?

An SSD would definitely boot faster, programs would start faster, maps would load faster. Although there are other ways to get rid of the "general slowness" and come close to a fresh install again, an HDD will never be as fast as an SSD in those tasks.

However your HDD definitely isn't responsible for stuttering and screen tearing. Neither a new HDD nor a new SSD will fix this.

Settings? Especially the stream makes quite a difference. 320*240 at 15fps runs on a toaster, 1920*1080 at 60fps means i7/Xeon minimum.
Also if you're going for minimum there will be fluctuation.