Under 20w from Xeon D is very hard. Remember the system powered off with only the AST2400 BMC up is already 4.5-5W. Add in two DIMMs will be at minimum 3-4W more for 16GB DIMMs and then drives and 20w is just not a lot these days, especially with 35W/ 45W TDP CPUs. Idle you can get into the low/ mid 20W range easily with the 35w TDP CPUs it seems.