Yes you can.
BUT you will be limited in the Graphics department.No room for expansion in 1U case. Some 2U racks have an expansion slot. Usually PCI or PCI-X not PCI-E for a modern graphics card.
If this is for a DJ rack or Band to play music while on break you dont need anything more than the onboard video.
Cost will be another factor unless you already have the parts and just wish to see if it will work. They are pretty much a very slim pc.
What about, say, a stock AMD CPU cooler (those block-shaped ones)?