I'd go with the Pass.
If you know anything about heat dissipation on heat sinks, the top mounted ones on some Clayton models are a not efficient at all for removing heat for Class-A heat dissipation.
You need vertical side mounted, and as many fins as possible. (thickness of fins are not important) surface area is.
I’ve made many very large pure Class-A amps >100w that heatsinks were not an option to use, as they would be as big as a coffee table.
I used a water cooled heat sink which was far better and cycled warmed coolant, through a slow fan cooled small radiator very effective but a very complex amp.
Cheers George