Cooling Cooler Master Elite 342 fans

[TobletDanillio]

I'm making a cheap NAS drive and have just got a Cooler Master Elite 342 for very cheap of a mate from work.
I want to put a fan in the back maybe side sized 80/90mm but not sure what to get I want them to be cheap ish but then its finished it will be on 24/7 so has to be good build quality.

for cheap I have found this;
linky

but I have seen an Arctic cooling F8 have the F12 myself I think they will be good;
linky

but what do you guys think?