Difference Between VS TFS Version

Hi All,

In our company we are planning to buy the Visual Studio Team Foundation Server. Can please suggest me which the best version to buy.

Please give the difference between this version.

VSTeamFndtnSvrCAL SNFL LicSAPk MVL UsrCAL - Partnumber = 126-00172

VSTeamFndtnSvrCAL 2012 SNGL MVL DvcCAL - Partnumber - 12601689

VSTeamFndtnSvrCAL 2012 SNGL MVL UsrCAL - Partnumber - 126-10690

VSTeamFndtnSvrCAL SNGL LicSAPk MVL DvcCAL - Partnumber - 126-00159

VSTeamFndtnSvrCAL 2012 SNGL MVL - Partnumber - 12501192

VSTeamFndtnSvrCAL SNGL LicSAPk MVL - Partnumber - 125-00113

Thanks & Regards

Kumar...