IMO is it an upgrade compared to the M2C, same sound just more details and more bass. I own a pair of Pk2s and it's a for sure it's a huge upgrade.
I've said it before, with limited edition earbuds like the ANV3s it's a no brainier. If you like either the M2Cs or the TM7s buy them. IF you do not like them, I see no reason why you would be not able to sell them at the same price you bought them or more. There are plenty of people buyers out there.