Here's an original build - https://pcpartpicker.com/b/tbkdnQ
Original PC ran a bit to slow - perhaps only changing HDD to SDD would have made system much faster, but I decided to swap CPU also, because I was starting to become suspicious about that Celeron. So I added new CPU - Pentium G4560 and new SDD - Samsung EVO850 256GB. Aerocool CS-101 case allows to mount 1x2.5" HDD+ 1x3.5" HDD + 1x5.25" optical drive or you can use 2x2.5" HDDs without the optical drive at a time. To use two 2.5" HDD's and 5.25" drive at the same time I had to mount separate 3.5"->2x2.5" installation frame (mounting bracket).
PC got much faster after that.
Next thing, that needed attention, was the noise coming from Intel stock cooler. I know, there's some good quiet CPU coolers around (and I am using one on the other PC - Noctua NH-L9i), but the mission was to keep costs down, as this is budget PC. Since G4560 CPU has relatively low TDP (54W) and is not used for demanding tasks, I went with Arctic Alpine 11 Passive and two 80mm case fans. These two 80mm fans push air through passive cooler (case is placed horizontally) and is silent when runing below 900RPM (they are not exceeding this value 90% of the time after I configured temperatures and speeds in bios correctly). CPU sometimes heats up to 52°C, but usually keeps below 46°C and idles at 38°C. When running Passmark tests it heated up to 56°C for a moment and that was the biggest figure I saw until now. Room temperature is about 23°C.
What is good about my new setup - PC got much faster and quieter. It's so quiet, that I can clearly hear PSU fan. So next challenge is ahead.
Update. HDD was the noise maker, not PSU - so I disconnected it while SSD space runs out and enjoy complete silence.
As many have mentioned before - best "performance for money" budget CPU.
Designed to work with CPU's up to 47W, it is cooling my 54W TDP CPU better than a stock cooler, perhaps also due to case design. CPU temps barely reach 55°C under load. Would use again. And again.
Solid built, inaudible up to 900RPM. Under load it sounds like mini V8 engine, so some of you may find this sound quite pleasing:)