Maggies - 4 or 8 ohms with sub amp in between?

Archived from groups: rec.audio.high-end (More info?)

AMC-3030 integrated tube amp. Runs 4 or 8 ohms. Using an NHT SA-1 sub
amp in between. (Sub amp runs speaker level signals and crosses to
Maggies at 120hz). I know the Maggies want 4 ohm and the tube amp can
do it. However the NHT sub amp is in the middle. I assume it wants 8
ohms(?). I also assume it uses a passive xformer inside to couple the
signal in the amp for the sub and cross over the Maggie signal. I say
it must be a xformer because the Maggies work with the sub amp off - the
signal passes right through.
So which tap do I use on my AMC?