I have seen a couple posts in some random places that say you cannot use an unlocked processor (K) with the 'H61M-P23 B3' motherboard. Can anyone verify this with a reference or explain their certainty? The posts in question all seem to state that a P67 board is required.
It is true, if you take this article about different chipsets as an example (one of the first results google showed).
about the H67:
and about the P67:
The board from your question only uses the H61 chipset, but regarding your question the answer is the same.