Fortunately the format is EATX so an EATX case will work and the screw layout is standard.
You will need to remove the HEX/TORX screws that are connecting the stock HP standoffs (meant to slide into an HP case).
XW9400 Motherboard Issues
Size: 12" x 13"
Proprietary Power Connector
Proprietary CPU Power Connector
Proprietary Memory Power Connector
Fan connectors are 4 pin so you will need some kind of adapter.........
For years I've always built cheap systems believing that there is little difference in more expensive components when it comes to reliability and quality, I generally believe this still except for Power Supplies.
I've always bought cheap cases with nice sounding 350-550W stock/cheap/crap power supplies and haven't had any issues for the most part until recently.
One such case is an NGEAR case with a 550W Optimax power supply, I always read that these supplies don't produce the........
I found that wattage/power consumption tool to be very useful, especially when you're worried that you're hitting the Power Supply's limit. You'll see very quickly that different CPU's, Graphics, Cards, HDDS use a wide range of energy. That tool can help you choose a build that won't stress or go over the maximum limits of your Power Supply.........