I have a 3rd PC haven't used for a while , recently been testing it out, it's a 5 year old i5 4670, Be Quiet Dark Rock cpu cooler, 8gb RAM, Corsair CX550 PSU, no graphic card anymore i sold it on. Long story short the 2 x 120mm case fans where very noisy running at 100% as connected to PSU, they're 3 pin so with my limited knowledge didn't want mess about trying to sort out how get them connected to 4 pin slots on motherboard. As i said this is my number 3 backup system and no gaming, nothing intensive at all will be done on it. I will passing it onto someone else as a nice gift to them and they will only run as browsing/music/movies about 5 or 6 hours at day and they like a quiet machine, so with me disconnecting the case fans it now runs nice and quiet and temps average around 29 to 33 centigrade according to all temp monitors i've used. I know its heresy and i'll probably be hunted down and lynched for saying this, but surely there is no need for case fans based on what the system will be used for and that at least its got a pretty decent cpu cooler with reasonable temps ?