Starwood Lurker addressed the benefits of Preferred Plus and Corporate Preferred in this thread.
http://www.flyertalk.com/forum/Forum74/HTML/005576.html
Indeed there is no mention of upgrades to suites other than Preferred rooms.
Mack2897, if this is your first experience with SPG, please give them a chance. They treat their elites very well sometimes even beyond the call of duty. I don't know if you've noticed him yet, but
Starwood Lurker is a valuable asset to the Starwood board here on FT and he's here to assist you if you have any problems.