Upgrade of SRM to 6.1 in a side by side config

Hi

I have a customer who has vSphere 5.5 (inc vCentre) and SRM 5.8.

We are looking to upgrade to 6 u2 (not 6.5 at this point as a couple of the hosts do support it).

The preference is to install a new instance of External PSC with a new vCentre server 6, rather than upgrade.  Can we build the new version 6 environment and build a new SRM 6 environment alongside the existing SRM 5.8 and migrate into it?

Thanks