I played Doom for a few hours yesterday, and temps are up about 4C from normal. So I'm running at 55C instead of 51C. You were right. It's hotter, but the result is acceptable. I can always take off the plate if it gets too hot, or I could just turn all my fans to full blast too.
The foam has made it a little bit quieter, but it's not enough. I'm looking into adding a resistor to the pump power wire, which will make it even hotter. But who cares about a few degrees when there's this eeeeeeeeee sound that's driving them mad?