Can't disagree with that.
Although I'm a little bit... well.. geometry. Like, if you have a flat 10x10" motherboard, and then as little extra stuff as possible, wouldn't you end up with a relatively rectangular case? (Like a minitower or any of a ton of
slim uATX designs.)
But you say you want a cube.
Making a cube to fit a uATX board means at
least a 12" cube, since you need a little room around the edges. The 13x12x15" 804 isn't all that much bigger than the minimum.
So if you want a uATX cube, which has gotta be at least 12x12x12, what do you want to do with the extra 8x12x12 of empty space? Or do you really just want a slim desktop style case like the InWin I linked? I guess I'm having trouble visualizing. Unless you mean you just would be happy with the 12x12x12 and
some internal expansion, but the 13x12x15 is oversized?
The HD-less version of the 304 is called the
Silverstone SG05.