Traced the issue to a headphone extension cable. Amp is fine and LOUD. Here's what I found for anyone else having a similar issue.
Was using a coiled hosa hpe325, the output with this cable is low on the 32R but always fine through UA apollo.
Plugged phones straight in, much hotter. I did not do this before, SHAME on me.
Tried straight hosa hpe310 and get the hotter signal. The straight/coiled effect is noticeable through UA apollo and through an external hdph amp, but not to the same degree, maybe 3db-ish. Apollo's hdph output is 300ohm, compared to 60 on R32.
Can't find data on the hosa cables but it's reasonable to think that the coiled cable has higher impedance and is mismatched to the 32R's hdph amp.
Lesson: signal path, halfway>test>halfway>test.