Probably only around 800. I'm running an unmodded machine at 800 I'm my office right now and the sound is manageable.

The mods are mostly just to (hopefully) lower the sound level since the plan is this will eventually go into the walk in closet which is freezing in the winter.

The 140mm fans are some extra stock NZXT fans I pulled off of an AIO radiator. If it's still too loud I'll throw some beQuiet or Noctuas on it instead.