Buy "Be quiet! Pure Power 12M" used or new?

I'm considering purchasing a new power supply. There's an offer on Mindfactory for €103 + €8.99 shipping for a new one. There's one on the classifieds, one from a private seller with an invoice for €85 including shipping, and one from a private seller without an invoice for €75 including shipping. The last two have been in use for about four months.

Be quiet! offers a 10-year warranty on its power supplies. Does the 10- or 9-year warranty also apply to used power supplies, or do I have to fulfill certain requirements?