No idea about TEC and D5, and you should know D5 is a damn good pump from what I understand.
Comes down to size and how much you want to spend.
I am not suggesting MAG over D5, only providing info on our product
You should not based any product purchase on what companies rep's say.
Yes, Mag is TEC safe. C-Systems parent company uses Mag design on there TEC units (not for PC liquid cooling).
Best I know D5 is XP safe, but again, ask guys at Danger Den.