If the only problem is being short of storage, it may be simpler to add another hard drive.
If you looking to gain more CPU cycles, etc by moving to a completely different server, you could use Novell's Server Migration utility. Officially, it is for migrating from NetWare to OES/Linux, but will migrate to NW6.5 as well.
http://support.novell.com/techcenter/articles/ana20030802.html
http://www.novell.com/products/mwizard/overview.html