You should go to a proper computer forum for this kinda stuff (Linus tech tips, OC3D & hardware cannuks are all good) but on the other hand I can give you some advice.
I'll take it as your spending roughly £900
I5 4670k- I7 is overkill for most things
MSI Z87-G45 gaming- Asus's line up for Z87 is overpriced and looks horrible. Plus spending so much on a motherboard has no benefit.
PSU, case- all great if you like them good value for money.
Hard drive buy a WD black- the velociraptors sound like a swarm of flies arrived . I know I had a 60gb one, back in the day.
GTX 660/660ti/7950, an aftermarket one though- this is we're the most money should be spent, a 6870 will be obsolete in two years.
RAM- meh don't really matter I've got 1886 but whatever.
You NEED cooling haswell kicks out a lot of heat it's onwards & upwards hear but be quiet cooler will server you well
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