kelpie
The B&W803 D’s are a hard speaker in the bass for an amp, and need one that is comfortable drive 3ohms for most of the bass and the even worse below 100hz where there is also a massive -65’ of -phase angle as well.
Because they are 91db efficient means they don’t need many watts into 8ohms, >100w will do. But that should double into 4ohms (200w) and almost double again into 2ohms (>350w)
https://www.stereophile.com/images/616BW802fig1.jpg
And the B&W 802D is just as amp demanding also
Cheers George