Should I Upgrade to OS X with Retrospect or stick with OS 9

[JStrickland]

I currently have Retrospect Workgroup 5.0.328 running on a Workgroup Server 9650/350 with OS 9 and ASIP 6.3. My network consists of 3 Windows 2000 PCs, 6 OS X 10.2.4 Macs, and 6 OS 9.X Macs. I am backing up to a Sony SDX-D700C AIT3 Tape drive. At this point the only reason ASIP is still on this computer is for the Print Server. Otherwise this computer is just acting as a file server and the backup server. Even with my fast tape drive, a complete backup of this network can take almost 24 hours. On top of that I am only getting about 150GB of data on each tape versus the 260GB rating. Would there be any advantages to upgrading this computer with a G4/800 upgrade card and upgrading the OS to OSX? Does Retrospect 5 on OS X have any advantages over running in OS 9? Will there be a possible increase in backup speed? I know this is a long shot, but might there be any improvement in file compression during backup? Any help would be greatly appreciated.