sql server upgrade to 2012 .how to select the hardware requirements?

we are currently having windows server 2008.we would like to upgrade to windows server 2012
for the installaion of Sql server 2012 
can someone please answer my questions

1.which physical blade should be purchased for the upgrade of Windows server 2008 to windows server 2012
currently we are using BL 465 c G5

2.how to choose how many processors that windows server will have?

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