i bought a refurb optiplex last week, its an i5, 7th gen. its a small form factor case so pretty small.
What could generate noise?
multiple case fans - this has none - only on on the cpu
CPU fan - the one on the cpu is practically silent
GPU card - the video card is built into the motherboard - so fan to make any noise
spinning hard drive - I have an 8TB installed - it generates very little noise, practially undetectable
I would recommend a similar configuration. To be honest, i didn't think it would be this quiet.
very happy with it so far !!
as a sidebar - in the event you decide to build your own from scratch, Noctua fans are known to be super quiet. Also, where applicable, get larger size fans and run them slower versus getting a smaller one that will run like an airplane propeller - LOL