Well, wha if you stuck with Solaris 8 for many reasons but need to get it on modern SPARC HW and better yet get it clustered? You also need MPxIO working with latest arrays, and if you could go with SC3.2 for free to limit costs that would be ideal...
Playground: 2x T5220, 1x 2530 SAS array, Solaris 10 U4, MPxIO, IPMP, Sun Cluster 3.2 with Zones agent, patch 126020-02 applied (support for Etude). Entire software is for free.
Then you install Etude - just two packages. Export your Solaris 8 root file system over nfs or create a flar archive. Now you create a Solaris Branded Zone with Solaris 8 emulation providing exported Solaris 8 or flar archive as a source and a moment later you have a working copy of your Solaris 8 system in a Solaris 10 zone - cool!
Now you configure that Zone under a cluster (couple of commands) and you got it clustered so you can switch that zone between systems.
So far so good. Next week more functional tests and some basic application testing. If it will go well then we will switch production to it.
Last phase? Create another Zone - this time Solaris 10 zone (standard one), put it under a cluster and migrate one by one applications between zones doing some cleaning at the same time.
In a mean time we will provide better reliability due to clustering, better performance due to faster storage, more RAM and more CPU power.
Not only it allows you to use recent HW and rapid migration, but since it's running on Solaris 10 you also benefit from technologies like ZFS (yes, etude zone can be on zfs), Dtrace, resource management, etc.
How hard is it to set-up? Actually very easy, way easier than you think.