The S300 is known for running hot.
It’s part of the design, and not an issue. In fact, if it isn’t getting warm it could be a sign of an issue.
The large heatsinks on the sides are there for a reason. Your setup looks fine so long as the glass isn’t being affected by the heat.
I’ll give you two guesses, and the first doesn’t count.
So many people in this hobby that think solid wood is an improvement over MDF or Particle Board, or that the complexity of a crossover circuit has anything to do with its quality.