Do Simaudio integrated amps run hot?

I've owned Simaudio I-5 LE and Simaudio ACE integrateds, don't know if they are similar to the one you're considering, but neither of them created any appreciable heat. Slightly warm on the top, as I would have expected.

I have a 600i. It's in a near field system and I don't crank it, but it runs cool. First ten watts are class A if memory serves. 

My Ace owners manual says 4 inches sides and back, 9 inches on top.

I have often worried about appropriate heat dissipating. High quality audio components (like Sim) are well built and pretty immune. If the company says 4K inches on the sides an 9” above… I would be certain” on either side and 3” above are plenty. If the back is open… you are good. 

I have two mono blocks….and I stack them. They have not gotten more than warm. NAD and McIntosh ran a lot hotter in my system and room.