You can enable nested environment using workstation. Then you can install ESXi in here and run all VM's on top of this. You can then add a vCenter, storage box based on ZFS (nexenta, freenas,...) and add additional VM's.
In this way you can shutdown the whole lab and use XBMC on Gentoo without problems. XBMC media player using ESXi will probably lag behind if you are going for 720p or 1080p video's.