I quess that , VAT is a kind of Taxation ... thats why they told you that the prices are final on .com sites ;)
As far as the mashine concerned , i think it is ok ...
CPU is quadcore ( but not really fast )
RAM 8 Gb is Ok ( but a litile bit more will be perfect )
I think you can handle up to 200 people online without laag ( it depends and on you server, if it have many custom etc etc )
Ps: Server4you is not really cheap ... i know other companies more cheap and better mashines ^^