Ok, so here is my idea.I am in plan to own file sharing hosting, so it would be for some small files, like 10MB max for the beginning and after that I will raise the uploading limit, so what kind of internet packet I should use with what kind of internet speed should be I mean Upload/Download and I want to build a server so my budget is 1000-1400 euros for building up a server and start to make the file sharing site. I hope I will get soon some good answers.
It depends on your traffic and on your budget. If you have a normal internet connection then you are foolish to buy a high end processor/mobo. If you have a T1 then your bandwidth will demand a more powerful server.
The bigest cost for you will be your HDDs and whether you will run them seperately or in a RAID array. I recommend that you stick with HDDs of 2 TB or less because there are still issues with Windows systems recognizing HDDs over 2 TB. Whether you want to provide SSD caching for the array is another consideration. If you go with 6 2 TB HDDs it will cost you upwards of $800 (and maybe even $1000).
As fir your OS I recommend Windows Home Server 2011 or Ubuntu.