Maximum PC

So over the years I've just bought computers from retailers and I've just modified them with different cpu's, gpus and such, now I'm thinking about building my own computer from scratch, but my main issue is finding a case. I'm planning to buy these:

Mobo - Gigabyte GA-Z77X-D3H
Gpu - Asus GTX 660ti (possibly a 2nd in the future)

So I was hoping someone on here would be able to give me a hand with picking a case for computer that will fit the motherboard and have enough room to fit a 2nd 660ti in the future when i have the spare cash to buy the 2nd one. I'm looking to spend a maximum of £40 on the case as I live in the UK.

I would just like to say thanks in advance.

How soon is "in the future"? I find 2nd GPU upgrades only viable if it's within a year, because by then, the next generation is usually on the horizon with something even better for what you could've paid for. Usually.

Case wise, it depends on how much space you're willing to give it. If you're going with MidATX cases, you should find something with breathing room in the middle for the graphics cards. While I won't stop you, I don't recommend a FullATX case mostly because it's a waste of space. Unless you plan on sticking 10+ drives in there.