Hardware should be tuned and adjusted depending on how many VPSes will be (or potentially can) be hosted on the Xen.
SolusVM Slave Software itself is rather modest in terms of the resource usage, it can be neglected.
Therefore, make sure that the server satisfies general minimum requirements for Xen nodes:
CPU: Must support hardware virtualization (Most modern CPUs support hardware virtualization. Intel processors that support hardware virtualization must have avmxflag, while AMD processors have ansvmflag.)
SWAP: 4GB (SWAP on a Xen server is used only by the host system itself. Xen PV and HVM guests use their own swap space, carved from the LVM group).