You could add a 670 later on, but generally speaking, it never works out. By the time one 670 isn't enough, the model you were looking at is discontinued, out of stock, or hard to get. You'd be due for a GPU upgrade anyway, so SLI and CFX are things you do on day 1 or you add the card a month or two later.
Is motherboard ready for i7 upgrade? I also remembered that he needs wireless connection. Also, this question might be a bit wide but, I have some knowledge in other parts, but motherboard is complete maze for me How to choose a motherboard? Maybe you can direct me somewhere to get the ropes?
What would he need an i7 for? The mobo is compatible with the i7, but for gaming, the i7 is just as good as the i5. Only get the i7 for video editing, Photoshop, etc. Just get DeusAres's/Why_Me's build and you should have no trouble.
I will put some work analysing and choosing a good computer guys. I only wonder for how many years (roughly) this computer would decent? I don't really get how fast everything goes
See that build I posted up above ? Add one of those cards linked in my post and call it good. That MSI GTX 670 for 320 quid will give you the most FPS but any of those other cards posted on there are decent. Google some reviews. That build allows you to add another one of those cards later on for a dual card set up.