In short, we can split everything into 3 seperate deals.

Q6600 between seamonster and irenic
irenic paid the full price. irenic claimed to receive the processor but not the receipt or the heatsink.
Conclusion: seamonster still owes irenic the heatsink and receipt

E2160 between irenic and seamonster
irenic claimed to have sent out the processor. However, the processor is claimed to have not arrived. Due to irenic not being able to provide proof of sending (lost of receipt), irenic is to bear the loss. seamonster has not paid anything for the processor. No refund needed
Conclusion: Deal is considered void. Case closed

E2160 between kucingfight and seamonster
kucingfight paid seamonster for the processor. The processor did not arrive. seamonster refunded kucingfight with compensation (very good dealer move).
Conclusion: Deal is considered cancelled. Case closed.

So after reviewing the 3 deals, 2 are "closed" except 1. seamonster still owes irenic the heatsink and receipt. Unless there is some missing information, that is the obvious solution.