nekulturny :
Seems to me like you're asking an awful lot out of an ITX.. Really, a lot. As in, its probably possible, doesn't mean I'd do it.
You aren't familiar with the small form factor enthusiasts, are you. ;p
We'll cram ridiculous amounts of power into incredibly tiny places, just because we can. (... that doesn't sound quite right, does it.)
Anyways, about 14 liters is enough for any very high end gaming PC. Smaller, if you're willing to make a custom case, or pay $300 for a specialty case.
Hugo, couple questions for you:
1) You want it to play games. What does that mean to you? High settings at 1080p on a 60Hz monitor? Or do you expect to be maxxing out games at 1440p?
2) Mini ITX is expensive. The motherboards are significantly pricier, the cases are pricier, and you sometimes have to buy 2.5" hard drives and SFX power supplies, which are much pricier. Consider micro-ATX, which is actually far LESS expensive than average ATX (because it's ATX with less materials, rather than having to be redesigned because it's so small), and can still be found in a pretty small form factor. The Aerocool Dead Silence is mATX, and not hardly bigger than a Bitfenix Prodigy. (Now, the Prodigy IS pretty big still, for mini-ITX, but I had a build in it that I often took to LAN parties, and as my carry-on when traveling.)