Capacitor, Z=R+I, Iz=1/(2*pi*f*c) and at DC, F=0, thus Iz=INFINITY, total impedance  is INIFINITY at DC, thus, in the case of Vbox Dynamic Duo, it functions to block damaging DC voltage (depening on topology since sum amplification topologies, especially tubes has no reference audio ground, thus caps is needed to remove DC and to restore ground).

So, for best RESULTS, BIGGEST capacitance is the best, added with quality caps with very low HYSTERISIS (NO AEC)..and for the fcuking best, NO CAPACITOR AT ALL! PERIOD!!

So to say using sum supreme high end leet caps make sounds nicer than no caps at all its only..COLORATION of sound, UN-PURE. However again..i always use decoupling caps at one stage of my system, preferably at the amplification input section (since the input stage of the amplifier can accept capacitive drive better than driing a capacitive load) and try to remove any other caps in between (since most DAC output stages has their own decoupling..which i always cabut).

For me, no caps sounds the best, very balanced and all...the best caps i haf now it oil impregnated NOS RIFA 3.3uF (each as big as 2xSize C battery) and its comparatively supremely better than the one i haf been using before, a 6.8uF metallized polyester, and still better than my 2.2uF wima polyester and sum 1uF polypropylene i haf..but still cant beat the transparency of CAP-LESS

...i talk too much..haha!