UPDATE: Turns out a shorter SCSI cable arrived today, and I changed cables. Well what do you know? IT NOW WORKS!!! W2K8R2 sees the changer (as unknown changer) and BE2010R3 sees the changer now, no problem. Both magazines are enabled and it works like a charm. Lesson learned: Be sure to check cables before you start to pull your hair out. Thanks to all who chimed in. 
Hello, Does anybody know if this combination works properly? I have read some horror stories about the drive being detected but not the changer, etc. Are drivers need for the card or does Win2008R2 install them by default? Is a Dell-branded card needed or does an LSI non-OEM work the same? Sorry for all the questions! Thanks!
LSI20320IE + PV124T (LTO3) + Win2008R2 + PE2950III