Pro-tip if your intake fans have filters on them (5 euros at any corner store):

Setup your cooling in the BIOS in such a way that you pump more air into the machine than you suck from the machine (essentially creating a little bit of pressure inside if you will). that way air will always blow out of the little holes in your machine rather than suck air + dust in. that way the only thing you'll ever need to vacuum are the filters.

Hah, I also just received some parts today. threw out the old i5 from ~2011, together with the mainboard and ram. now rocking a (woooow) Athlon 3000 in there. SAS controller for all the drives is on the way, we'll see how far I can push this thing.

@Hendrik Peter thanks for the tip! Now that I verified the thing just purrs along as expected I think I'll actually start making it into a bit more of a powerful storage server and I think for that a better chassis with a thought-through airflow would be a good thing. Because omg did I get dust out of this one. :D