Question 1) Why won't you be able to install Vista in English?

Anyway
Other than that onto OS choices.

IF you use XP then you will be limited to using Horizontal span to get good FPS. With 2 or even 3 monitors, this won't pose a problem. But, if you decide to get a fourth monitor, then you'll probably want to mount it above the existing monitors. This is where Vista comes into its own, it treats each monitor individually AND doesn't suffer the FPS hit like Dual-view does in XP.

4GB of Ram, you'll need a 64 bit OS, so Vista 64 is my recommendation to you. You'll suffer a slight overhead, but nothing too excessive I wouldn't have thought.

Try and order stuff online, from a company that'll ship it to your country.