Yes, nested virtualization is supported. You may create virtual machines on your VPS hosting.
Most of our servers use CentOS 6 as host system. For creating x86_64 virtual machines, you have to install CentOS 6 or Debian 7 on your VPS hosting. If you want to create x86_64 virtual machines on latest sytems like CentOS 7, please submit a ticket, and we will migrate your VPS hosting to a server which host system is CentOS 7.