Under A/UX as the OS, Mode 32 is unnecessary (A/UX somehow by-passes the SE/30's "dirty ROMS"), though an SE/30 is a tad slow for A/UX. Or it's slow when running version 3, at any rate; I have never tried versions 1 or 2. You do, however, actually need the extra RAM for running A/UX. 8 x 4MB chips would do the trick - and 32MB RAM is plenty.

I like the SE/30 running System 6 myself, under which the machine is nice and snappy and suitably minimalist, but it is quite something to have a full-fledged UNIX with a virtual System 7 environment running on one of the little things.