Never heard of VMs taken on any EVC features, so I'll investigate further. If that turns out to be a problem then I'll just need to do a cold migration from ESX 4.1 host to ESXi 5.1 so that way upon boot up the VM takes on the new hardware and doesn't go by the previous hosts hardware features, etc.
I would rather just vMotion them into the new host servers, so I'll investigate this further by calling our VMware support to clarify my plan before moving forward with it.
Again, thanks.