OK, so me and my friend stayed up all night looking at different components and this is what we settled on:

The price of these components (and Windows, which is quite expensive as well) combined is around 27000CZK - I currently have 21,084.20CZK, so that's still quite a bit short for this combo. I looked and you can't really buy these components much cheaper than this here and if you go for cheaper components, you also go for much lower performance. You'll also notice the absence of a dedicated GPU - I decided to go that way in favor of a more powerful CPU, which is much more important for video work. If I wanted to lower the price, I guess I could do with just one HDD but having two would be beneficial for rendering and encoding and I'd still be a bit short (and smaller HDDs wouldn't come much cheaper if I don't want to buy Seagate).

So, what do you guys think?