I'd go check and go with each component's specific manufacturer's advice.
For example, I run a Pass Labs X250.8 amp. The dealer reported that he felt that locating the amp in my wood rack, with 4" of clearance all around would be sufficient, but it wasn't at all! I moved it out and picked up an amp stand, with plenty of space for the amp to breath.
Here's what the Pass Labs website has to say, "Heat and Ventilation - The X.8 and XA.8 amplifiers consume quite a bit of power during operation and convert most of it into heat. Pick a location where the amplifier can get some fresh air to remove the heat. Do not enclose the amplifier in a closed cabinet. Give it lots of space." I can attest that the X250.8 puts out a ton of heat, which is great for our dedicated music room (and the room's plants) in our bitterly chilly NH winters; not so great in the summer, that's where the mini-split comes in to play.