Be careful, there are no load graphs done on these that I could find, but it’s said the 803’s have a minimum impedance of 3ohms in the bass, which could look similar to the 802’s graph of impedance and -phase angle
This sort graph indicates the use of an amp with decent current ability in the bass and even up to 1khz.
To get the very best from these speakers, I’d be looking at amps specs that can "almost" double their
8ohm wattage (eg100w)
to almost double it into 4ohms (eg200w)
and almost double it again into 2ohms (eg 400w).