Don't you find the R720 to be astonishingly loud for something to keep at home? 1U/2U size servers are not really designed to be quiet. Maybe if it's way out in a far corner of your garage or basement somewhere...
My home test xen hypervisor is an older Dell desktop mid-tower workstation dual socket/8-core xeon, because it's reasonably quiet.
You can either manually control the fans with some form of IPMI tools or by disabling the fan offset (needs to be done every reboot though). Then it is actually very bearable, asuming you have good ventilation around it.
My home test xen hypervisor is an older Dell desktop mid-tower workstation dual socket/8-core xeon, because it's reasonably quiet.