I am in the process of purchasing an SSL certificate for our Hybrid Exchange Server.  I created the request in the Exchange Management Console.  Now I am on the Thawte site for purchasing the SSL cert and it is asking me to "Select a server platform".  Normally I would select IIS6 or 7, but since this cert request was generated in the mangement console what would I select?

Also, I am looking at purchasing the SSL Web Server Certificate which is less expensive than the SGC SuperCert, but do not know if I can.   Can you give me some advice on which certifcate or third party CA I should use for the hybrid certificate?