I am sorry, i do not know the dissipation rating, i got it from a computer i found in a dump while looking for parts in my quest into making a jet engine.
It is a CPU heat sink, it should, in theory be fairly good quality,(came with a fan if needed) but that is not very scientific i agree.
I would like to try the one tube version, should help not having to "match" tubes plus it is overall less expensive.
However, i am afraid i dont have the competence to modify the design that will match the single tube modification.