Not to derail the OP's post, but curiosity overwhelms me... show me another standard layout, mATX case that holds 6 HDDs that is smaller. Sure the Mini is nearly as large as a small ATX case... the mATX form is only marginally smaller than the ATX, but it's smaller than almost all of the other mATX cases I looked at.
No, surprisingly, the Node 304 takes a standard ATX PSU. Now that I'm looking at other images of the Node, it does indeed hold 6 HDDs... in fact, it looks like quite a marvel of design and engineering! ...but, understandably, it's all jammed in there.
If it's nearly the size of a mATX case then what is the benefit of this case over mATX other than being a little smaller? If you absolutely need the extra space due to it's location, I get it. But most people have their NAS out of the way (Mine's in the laundry room) where it's size is really unimportant. Granted, the mATX market is still expanding and is much larger than what it was when I bought my ITX rig, but at the end of the day I still see having more options available with mATX as opposed to ITX simply for the greater abundance of motherboard/cpu configurations available, and having more expansion slots (if needed). And you also have a little more space to work with during hardware installation. It seems like a well built case, but for all intents and purposes it's just a mATX case that takes an ITX board.
The way I see it is that the benefit of ITX is compactness and if you're not getting that, then you might has well step up to mATX and open yourself towards the benefits of that.
Now I've done some searching myself and here is what I have found....
Apevia X-Q Pack (mATX Desktop) 3x 3.5" + 2x 5.25" bays. = 5 HDD bays with adapters.
Pretty simple design and not much larger than the fractal design node.
Lian Li PC-V351B (mATX Desktop) 3x 3.5" + 2x 5.25" bays. = 5 HDD bays w/adapters
Nicer design and more appropriate for a NAS, but still not quite enough HDDs.
Silverstone SST-PS07B (mATX mini tower) 6x 3.5" bays + 2x 5.25" bays = 7 HDD bays w/adapters.
Not exactly huge, but it's about 45% larger than the fractal design ITX case. Seems to be well designed and backed by good reviews. It also has the simple, but attractive NAS-like appearance that I assume the OP is going for.
If I were looking for an mATX case for a NAS, this would be my choice.
Now if you're trying to save a few bucks you could take a look at this...
Apex TX-606 (mATX tower) 6x 3.5" bays + 2x 5.25" bays = 7 HDD bays w/adapters.
Although this is considered a mATX tower, it's actually slightly smaller than the Silverstone case above, and it also supports and additional 2.5" bay which could be useful for an OS drive if needed which of course could free up 3.5" bay. Only thing is that I'm a bit weary of cases in this price range as they can be very hit and miss and I generally don't do it unless it's got a number good reviews to back it up.