Hosts, Guests, and Domain

I have two server boxes. 
Server box #1 I've loaded Windows Server 2008 as the (hyper-v) host OS, plus SBS 2011 as a guest OS. 
Server box #2, I want to load Windows Server 2008 as the host OS and a guest OS of Windows Server 2008. 
I'm assuming that the host OS on server box #1 can just stay on 'workgroup'. SBS 2011 of course is a domain controller for my new domain. On server box #2, I want the guest OS to be on the same domain as SBS 2011. Should I put the host OS on server box #2 on the same SBS 2011 domain, leave it on workgroup, or does it matter?
Thanks!