They are indeed not cheap especially the larger units. All are about as easy to use as the next one, so don't focus too much on the brand. Make sure to buy a unit with more slots than you need if you're ever thinking of expanding unless you want to spend an eternity when doing so.
(Specific to my Synology) They're only silent for as long as the CPU fan doesn't collect too much dust, after which it's a tossup between the fan not working at all and OMG dafudge is that horrid noise?! (a.k.a. add some dust filtration)