[Serusers] SER question - Has anyone been able to successfully use Polycom SIP phones with SER?

SERusers, I am working on a pilot for SIP and am planning to purchase a server and install SER on it. I need to purchase several SIP hardphones to test and wanted to see if anyone had any recommendations. Are most of the "SIP compatible" phones out there still proprietary to a particular server? The phone in particular I was looking at is the Polycom Soundpoint IP 600, which won the "Editor's Choice" in a review by Network Computing http://www.nwc.com/shared/printArticle.jhtml?article=/1416/1416f2full.ht ml&pub=nwc . If this will not work, does anyone have ANY hardphone recommendations? Polycom says their product has only been tested with Broadcom's SIP server. I apologize for being such a newb...I am still trying to read up on SIP and understand the big picture. I appreciate any help or feedback. Thanks, Scott