If the goal is ''as small as possible'', then N1/K3/BC1 style cannot be beaten. The JX1 style is definitely, relatively speaking, more 'complicated' and larger than the traditional test bench style.
Below is a pic of my JX1 system. That was my C14S there. The system was very stable. I think that is why the base needs to be large enough to provide stability (rather than to provide the space for an ATX PSU). Remember that this style also caters for having watercooling hanging on the back, which can add some more weight.
IIRC, besides the JX1, the other one or two similar styled test bench that I saw also have the base this large. (If I come across them again, I will post them here.)
[MEDIA=imgur]a/pOHwSPx[/MEDIA]
There is yet another style of open test bench, in the form of A4 sandwich style. Basically, it is an A4 sandwich case without the enclosure shell. Of course, this will be even more 'complicated' and larger.
Ultra Civiliz A4-X is a prime example.
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