A:Answer itsRG,
In the current configuration, which can be subject to change, this system comes with a single PCI-E x1 expansion slot open. In regards to the power supply, there is still room to add additional hard-drives and PCI-E devices.
There is two total RAM slots, one is being used bringing the system to 16GB's, which leaves one open slot, for a total expansion of up to 32GB's total.
Thank you,