Just the bench with an itx board is 230*190*105mm (w*d*h) so roughly 4,5l without considering heatsinks, gpu and ram.
Then again the silentmax ist rather big 210* 135*160mm (w*d*h) soooo roughly 4,5l. Sadly the seller of the cpu cooler has yet to send out the cooler...
I guess the total volume...