The above figures can't really be compared. The W164 is measured using the VDA method. I have not yet seen a US cargo volume figure for it, other than a preliminary one, published in Autoweek and giving 77 cu ft.
To compare, here is the number from www.volvocars.de:
"Bei vollständig heruntergeklappten Rückenlehnen der zweiten und dritten Sitzreihe: 1837 Liter*
*VDA-Messmethode"
The equivalent number for the W164 with the second row folded, but not removed, is 1830 Liters.