- Will be used for NAS and HTPC (Synology/QNAP don't have CPUs that can transcode or run windows apps I need)
Personally im not too much into doing an all in one solution in HTPC+NAS/Server, as you will add unecesary noise like hdds spinning to where you will be seeing movies, extra fans to manage the load, etc.... but it can work out fine as long as you accept the compromises.
- Quiet of course
Quiet will depend a lot into what components you place in, and how you run it / use it.
This is fine product for a saving space into a server and have the convinience of hotswaping. But it might leak the noise of the hdds out. Im not sure its a good idea for HTPC, but for a server elsewhere would be fine.
- As small as possible given the requirements.
This is another why i like a server separated where space is not restricted or doesn't bother the aesthetics of the rooms. And htpc can be build really small now a days even there are some fanless options.
This would be my suggestion, since you want small and hold at least 5hdds,Fractal Design Node 304 FD-CA-NODE-304-BL Black Aluminum / Steel Mini-ITX Tower Computer Case
No 3x 5.25 bays, but its a relative small mini ITX case with a chance of placing 6x 3.5 hdds and standard PSU (limited by the lenght). You could go with a mobo like ASUS P8H77-I
(six internal sata ports) + CPU will depend a lot into your desired transcoding software and amount of devices you will want to have at the same time, the nod304 has a nice space for decent sized coolers, it can even take some tower coolers. A PSU like Seasonic SSR-360GP
should be cheap and decent option for it, also reviewed by SPCR in case you are interested, Seasonic G360 PSU: High efficiency & performance, low price
Some other suggestions to look into,SILVERSTONE Black Aluminum / Steel Grandia Series SST-GD08B ATX Media Center / HTPC Case
Doesnt have your desired 3x5.25, but it has a more static pleasing look for how components look in HT, it can hold 7x 3.5 hdds and can house ATX mobos and standard ATX PSU (but with limitation on the length). Has been recently reviewed by SPCR in case you want to read more, SilverStone Grandia GD07 & GD08 Media Center CasesFractal Design Black Aluminum / Steel Node 605 FD-CA-NODE-605-BL ATX Media Center / HTPC Case
Similar to Silverstone, again no 3x5.25, but can hold 4x3.5 hdds depending on the other hardware you have inside. SPCR also reviewed it in case you are interested on reading more, Fractal Design Node 605 HTPC Style CaseFractal Design Define R4 Black Pearl w/ USB 3.0 ATX Mid Tower Silent PC Computer Case
Again no 3x 5.25 slots, but its a nice stadard mid tower than can hold atx mobo/pus and can hold 8x 3.5 hdds, while not hotswapable they very easy to access and cable management is very nice, can hold big coolers like HR02 macho and its laid back style might fit good on ambient. Its predecesor, the R3 which is very similar, was reviewed by SPCR, Fractal Design Define R3 ATX Tower
. Slightly smaller (only 6hdds) similar in design, there is also the Define mini (micro ATX), also reviewed by SPCR, Fractal Design Define Mini MicroATX Tower
Some server chassis,ARK 4U-500-CA Black 4U Rackmount Case 3 External 5.25" Drive Bays
Has your desired 3x5.25, its not super small but not huge as other server chassis. Rosewill RSV-R4000 Black 1.0mm SECC, 4U Rackmount Server Chassis 8 Internal Bays
Has your desired 3x 5.25 slot for your hotswapable hdds, beside has slots inside to hold another 8hdds, its not small but not huge either for what a server chassis can reach, for its price is pretty decent.Rosewill RSV-L4411 Black Metal/ Steel, 1.0 mm thickness, 4U Rackmount Server Chassis, 12 SATA Hot-swap Drives
More expensive than the above, but comes with 12 hotswapable 3.5 hdds slots, this makes up for the price difference easily, and will give you room to grow for the future without spending much money on hotswapable cages.