Cheap gaming computer building

Don't worry too much about posting in pounds, it's pretty common so people are reasonably familiar with it. Plus, the Uk version of PCpartpicker is pretty solid.

Ignoring your budget slightly, this is a rough outline for a "standard"ish Intel overclocking build.
PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-4670K 3.4GHz Quad-Core Processor (£173.82 @ Aria PC)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£23.90 @ Ebuyer)
Motherboard: ASRock Z87 Extreme4 ATX LGA1150 Motherboard (£111.88 @ Amazon UK)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory (£54.92 @ Amazon UK)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive (£42.99 @ Amazon UK)
Video Card: Zotac GeForce GTX 760 2GB Video Card (£184.99 @ Amazon UK)
Case: BitFenix Shinobi ATX Mid Tower Case (£49.90 @ Amazon UK)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply (£49.36 @ Aria PC)
Optical Drive: Samsung SH-224DB/BEBE DVD/CD Writer (£11.98 @ Ebuyer)
Total: £703.74
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-01-03 23:50 GMT+0000)

There's a lot of scope in there for customisation, and in some ways it's a little light on graphics relative to CPU, but it's pretty solid thing to work from.

To address a few concerns directly -

Bundles can be good, but often they aren't terribly well matched. If you want both bits, and it's a good deal, then great, but don't end up buying something just because it's in a deal.

If you don't want to overclock, then the K-series processor, Z87 motherboard and CPU cooler can all be downgraded to cheaper models, or in the case of the cooler, removed entirely. It can present a much better value solution for you.

The cooler I stuck in is the general good budget recommend. It's great value and will give you decent OC potential. If you wanted to spend more, then something like a Noctua NH-D14 or Phanteks PH-TC14 are about as good as you can get in air coolers. Honestly, at your budget level it's hard to look past the value of the 212 Evo.

I'd skip the 4Gb 270X, it just doesn't make financial sense. The extra memory is highly unlikely to be useful, even in a multi-graphics card setup. At that price, it's too close to GTX760, which is a better performer.

Memory is pretty straightforward. You can go faster than 1600Mhz, but only if the price is right. Otherwise, there isn't a huge amount of harm in sticking to 1600Mhz, it'll work with basically all systems.
Quad channel isn't something to worry about as it's not available on mainstream systems. Dual channel requires using compatible memory in matching pairs, like the 2*4Gb kit I linked.

A case is subjective, you basically should get whatever you like. I like the Shinobi a lot because I've used it before, and it works for both "showy" and more understated builds pretty equally. In the same price range the Antec Three Hundred Two or Fractal Design Core 3000, all of which are slightly similar in design but very solid budgety cases.
As for fans, it's probably best to narrow down your build and see how it works first. You can add fans pretty easily later on to reduce temperatures once you start overclocking. Most cases come with an intake and an exhaust, and once you have these you don't need a huge amount extra, though it depends on the case and what you are using in it.

If you want to give yourself a bit more headroom on the PSU, and pick up semi-modular cabling, then I'd suggest the XFX XXX 650 for £70, but the system should run absolutely fine on the 550W. In the UK there aren't really any other viable alternatives without spending quite a bit more money, in my opinion. For reference, the main component that dictates power consumption is the graphics card, followed by the CPU. For most mid range cards, even with an overclockable processor, a 550W PSU is plenty.

Oh, and the keyboard+mouse thing is a subjective thing, but I'd definitely suggest spending a bit more on a mouse for gaming. I've always been happy with a cheap keyboard, but a cheap mouse can be pretty frustrating. It's up to you of course, but it's worth a think. At least at £10 (ish) it's something you can toss if it isn't working out.

PCPartPicker part list: http://uk.pcpartpicker.com/p/2vajx
Price breakdown by merchant: http://uk.pcpartpicker.com/p/2vajx/by_merchant/
Benchmarks: http://uk.pcpartpicker.com/p/2vajx/benchmarks/

CPU: AMD FX-8350 4.0GHz 8-Core Processor (£137.00 @ Ebuyer)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler (£23.90 @ Ebuyer)
Motherboard: ASRock 970 EXTREME4 ATX AM3+ Motherboard (£76.87 @ Amazon UK)
Memory: Patriot Viper 3 8GB (2 x 4GB) DDR3-1600 Memory (£54.92 @ Amazon UK)
Storage: Hitachi Ultrastar 1TB 3.5" 7200RPM Internal Hard Drive (£41.40 @ Aria PC)
Video Card: MSI Radeon R9 270X 2GB Video Card (£153.98 @ Dabs)
Case: NZXT Source 210 Elite (Black) ATX Mid Tower Case (£38.65 @ Scan.co.uk)
Power Supply: Corsair CX 600W 80+ Bronze Certified Semi-Modular ATX Power Supply (£57.67 @ Dabs)
Optical Drive: Lite-On iHAS124-04 DVD/CD Writer (£13.18 @ Scan.co.uk)
Total: £597.57
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-01-04 00:15 GMT+0000)

My build is definitely more of an "Intel overclocking build" template than one tailored for your budget. If it were me, I'd probably skip overclocking and refocus into graphics etc, as that is going to give you a better return in gaming performance. Hopefully it's all helpful info though.



In short - yes. Cheap Z87 boards lack the features to truly justify the Z87 tag. You can save money here but if you want to overclock, it really doesn't make sense. Right now I think the Extreme 4 or Asus Z87-Plus are both pretty good options, but you are looking at the same kind of price for both. They are both well priced, good overclockers, and have full support for two graphics cards should you want to double up somewhere down the line.



The NZXT Source case in EcoMCGs build is a pretty solid budget option, but honestly spending much less than £50 doesn't often make sense as you'll run into issues with build quality. However your build works out, it's not going to be a bargain basement one, and so going with a solid case is a really good idea.
In addition to the ones already mentioned, check out the Corsair 200R/300R or Antec GX700.
My pick would still be the Shinobi or Antec 300, I've used both and was very happy with the results. The Shinobi in particular has the feel of a much more expensive case in places.