The iMac Pro was effectively silent when it was new. Or at least it was in all but the very quietest environments. Mine has gotten noisier over the last 4+ years. It's now situationally silent. I've heard the same from other long-term owners.
Given that shift I'm concerned about starting this process again with a machine that's a bit louder to start. A 2 dB difference is, I'm told, on the edge of perception, but it's not in the direction I'd hoped. Then there's the sound character issue that WhiteHawk mentions. I'm going to wait for reactions from users and reviewers this time.