Greetings,
Welcome to the forum.
I am not a HP employee.
HP may deploy modified front panel motherboard (MB) connections that don't work with retail cases. HP may also modify (MB) front panel USB pinouts.
I don't know if your MB is modified or if it adheres to standard ATX MB specs.
I don't recommend installing HP MBs in retail cases. This procedure may or may not work depending on what you have.
You can upgrade the graphics card. You have a 500 watt power supply.
Pick a new graphics card. Then compare the length of the new card for MB clearance and case clearance and the card's power requirements to your HP power supply.
Installing a AIO liquid cooling system requires removing the MB to install the back plate.
I would stick with the current system.
Build a PC when you are ready to upgrade.
it's your call.
Regards