But enclosed in a box without much airflow and those temps are going to creep up over time. And take even longer to cool down. Hopefully there’s fans in the bottom or side. Because one exhaust is not great for even just the heat from those hard drives.

I think the best way to handle airflow out is to have a turn or two on the intake/exhausts for the noise to get trapped. I personally just put mine in my basement though. That limits the sound pretty well.

All of those hard drives will produce quite a bit of heat just sitting idle.

They usually do transcoding when you watch a movie or so. Depending on hardware that may heat it up a bit. I guess if it would have heating problems then OP would have resolved that already though.