I'vbe built a couple of mate's systems in Prodigys recently, and I have to say, on ITX, things are a lot worse if you skimp out on components.
The cheaper ITX boards I've found offer next to no overclocking abilities. My mate's gigabyte has no voltage control options, and another mate on an ASrock sees similar things.
Also, with the power supply - cabling will be an absolute nightmare with a non-modular power supply.
Both mate's PCs I've built, we've used a Silverstone Strider 500w -
http://www.scan.co.uk/products/500w...onze-sli-crossfire-eps-12v-quiet-fan-atx-v23-
The first didn't use the short cable kit, the second did.
Without it, it makes things quite messy. You have to awkwardly put wires to the side of the PSU, and when you have cables having to come up for power to the motherboard, it does make things very awkward. The second did use the short cable kit:
http://www.scan.co.uk/products/silv...-cable-set-for-strider-series-psu-100-modular
That made things a lot easier, but even with those space is still tight.
I'd go with the P8Z77-i, 3570k and 500w silverstone strider.
An H100 will make things look a lot better than an h80, so I'd try and push for that, but if you need to save up a little more, even if it means running off stock for a few weeks/months, I'd try and push for an H100i.
Lastly, the graphics card...
Depending on how soon you're planning on building this, I don't really think we're able to recommend one. I'd say try and go for a 7950/7870 at the moment over the nvidia equivalents, but the next generation cards will be out in a few months, so it may be worth waiting to see how they perform - and even if you don't get one, the older versions should hopefully go down in price.