v9.x is no longer sold by Veritas. v10 is the current version
You can probably find some v9.0 or v9.1 serials (they both use the same serials) on EBay or one of the other Auction sites. I'm not convinced that v10 offers much over v9.1 myself. About the only thing that would tempt me is the Synthetic backup feature. If you do a fulls and Incrementals, Synthetic will produce a file based on the last full and any later incrementals so that you only have to do one restore to get back to where you were.
Upgrade from v8 to v9 should be no problem. You will need to re-install any Remote Agents that may already be installed on W2K servers or workstations.
Personally, I've never used IDR. The gain in recovery time is not that great compared to manually recovering, and I've seen WAAAAAAY too many problems reported here on the Forums to trust them.