Relax then buddy, in the virtual environment you'll have lots of flexibility. It's really easy to clone machines and bring them up and down, i won't say quickly, because for some reason, my SIMS server takes a few minutes to Power On, but it does in the end.
I'd recommend doing a P2V conversion and create a virtual clone of your current set up. Then you can experiment with making a new server. You could in fact make two, one on each platform, and ship the backups over daily, so if anything goes wrong you can always revert to the other version.
snapshots FTW :D
My experience of P2V with MSSQL is not a good one. I'd much prefer to do a clean migration this time - you know how legacy stuff builds up. The existing server has been running for about 6 years now.
That's the exact reason i ran a converted box. I wasn't confident legacy stuff wasn't going to stuff it up if i removed it.
To be honest, setting up a new SIMS server is really easy. The hard part is installing windows + sql and patching it up. After that running the install CD and / or restoring a database is SIMSples :) the only extra fiddling to make it live, is making a share and publishing and open up the firewall ports.
Clean migration shouldn't be a problem either. I wouldn't be concerned about changing to another server version later, it's seriously straight forward. You're better off staying on the tested platform for a bit, in case there are any anomalies as yet undiscovered.