Thanks for the reply. If I were to choose between a new CPU (4690K or 4790K) and a motherboard or a GTX 980. What would be the sane choice? I'm thinking that a new chipset and more powerful CPU would benefit me more in general while also giving me a big boost in gaming sometimes. I bet the SATA-controllers on a new Z97 chipset for example are far faster than on my old Z77 one.
Sorry to be a downer, but I'm going to advise you against upgrading for the time being. I personally think the sane choice would be to stick with your current i5 2500K and GTX 970.
Both Z77 and Z97 have SATA 3.0 ports, it's just that Z77 doesn't have as many of the high speed 3.0 ports that Z97 does. Still, as long as your SSDs are plugged into your Z77 motherboard's SATA 3.0 ports while your hard drives are on the SATA 2.0 ports, you're already more or less getting the best performance.
You won't notice much of a difference plugging in your hard drive into a SATA 3.0 port compared to a SATA 2.0 port.
When it comes to upgrading the processor..
the 4690K is only around 10% faster than your 2500K. Nearly all games save for a few examples don't really take advantage of more than 4 processing threads, so the
4790K wouldn't be much faster than the 4690K for most games. Even for a recent CPU-bound game like GTAV,
you'd only see a marginal increase at best going from the 2500K to a 4690K or 4790K. That benchmark was done with a single Titan X, so I think it's a somewhat more reliable result than SLI GTX 980s. Resolution may matter as well, so that's why the result differs from what Crisium posted.
It's a similar story with your GTX 970. If you already have a GTX 970, it's also hard to recommend upgrading to the GTX 980.
That's a small performance leap for a lot more money. If you have a decent GTX 970 with a good cooler,
you could overclock that to match stock GTX 980 speeds, that's how close they are in performance.
It's your choice if you want to upgrade, but we're just trying to say that it's not a very good use of money. Spending $300~400 on a 4th generation Intel quad core processor and Z97 motherboard to replace your old Intel 2nd generation quad core processor and Z77 motherboard nets you maybe up to 10~15% performance increase at best. If you feel the need to spend some money, perhaps you should wait a few months for Skylake processors and Z170 motherboards, at least upgrading then will be a somewhat better proposition because you'll be going with slightly better future-proofed parts. Skylake/Z170 will use DDR4 RAM and the new CPU socket 1151 which is incompatible with existing Z97 processors, and I'm expecting new technologies like USB 3.1 and USB type C ports to be more common on newer motherboards.
You said you were experiencing stutter? How bad is it, and how hot is your system running? Maybe better cooling would be worth spending money on for a more stable experience. What are your system specs?
How about something like this?
The i3 will get better performance than the 6300 or the 8350 in most games and the motherboard provides an upgrade path if you save up for a Haswell i5 or i7 in the future. It's also hyperthreaded so it's 2C/4T. So the games that require quad core CPUs read it as such. Of course, you could drop the GPU back down to a 270X or 260X and get a cheaper case if you're hard set on your price window.
If you're dead set on an AMD CPU I'd wait until next year and see what the new Zen cores bring to the table. As of now, though, the AMD CPUs are not worth the cost if you're starting a new build. If you already have an AM3+ motherboard then maybe forth just getting an AMD CPU instead of buying an Intel CPU/Mobo combo... MAYBE..
PCPartPicker part list:
http://uk.pcpartpicker.com/p/yGJhLk
Price breakdown by merchant:
http://uk.pcpartpicker.com/p/yGJhLk/by_merchant/
CPU: Intel Core i3-4170 3.7GHz Dual-Core Processor (£89.90 @ CCL Computers)
Motherboard: ASRock Z97M Anniversary Micro ATX LGA1150 Motherboard (£66.83 @ Amazon UK)
Memory: Kingston Fury Series 8GB (1 x 8GB) DDR3-1866 Memory (£41.69 @ Amazon UK)
Storage: Hitachi Ultrastar 1TB 3.5" 7200RPM Internal Hard Drive (£29.99 @ Aria PC)
Video Card: Gigabyte Radeon R9 280 3GB WINDFORCE Video Card (£148.10 @ Amazon UK)
Case: BitFenix Phenom M Midnight Black MicroATX Mini Tower Case (£62.80 @ CCL Computers)
Power Supply: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply (£57.98 @ Amazon UK)
Total: £497.29
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-06-07 11:28 BST+0100
Your advice is solid, but I have some recommendations for your build.
That specific Hitachi hard drive is an older model dating back to 2007 and it uses an old 5 platter design. Not that the number of platters necessarily makes it bad, but it is older technology. It works and it's cheap, but I'd recommend the newer
Toshiba 1TB model (£38) even though it costs a bit more. Also,
for £158 there's the XFX R9 280X instead, might be worth looking at since it's so close in price, especially if you can cut costs elsewhere.
I don't mean to butt in and I hope you don't mind the alternative build I'm listing below. Your build has a much nicer case, better motherboard, a modular power supply, and is better suited for future parts upgrades and overclocking, but the build I'm recommending below has stronger performance for a similar price.
@Stilton Disco, if you do not plan to do any processor overclocking, it would be possible to get an better performing i5 processor by going with some alternative parts. It includes the R9 280X but
if you go with the R9 270X instead, the same build will cost about £450.
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i5-4590 3.3GHz Quad-Core Processor (£144.97 @ Amazon UK)
Motherboard: ASRock H81M-HDS Micro ATX LGA1150 Motherboard (£38.17 @ Scan.co.uk)
Memory: Kingston Fury Series 8GB (1 x 8GB) DDR3-1866 Memory (£41.69 @ Amazon UK)
Storage: Toshiba 1TB 3.5" 7200RPM Internal Hard Drive (£37.97 @ CCL Computers)
Video Card: XFX Radeon R9 280X 3GB Double Dissipation Video Card (£158.81 @ Scan.co.uk)
Case: Fractal Design Core 1000 MicroATX Mini Tower Case (£22.49 @ Scan.co.uk)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply (£47.99 @ Scan.co.uk)
Total: £492.09
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-06-07 11:59 BST+0100