lots of good input already.
First thing that comes to my mind for warm rich sound with a little bulr... slight "bass halo" or whatever, is Neve. not necesarily any processing, just run thru any one of the old line amp, compressor or EQ modules 1272, 1271, 1073 1066, 2254 etc (with the class-A output circuit). There is DC flowing thru the output transformer in that circuit and it does something unique to the low end. by the way some of the more popular neve gear like the 1081, 2087, 33105, 33609's, etc have a different circuit and sound quite different in the low end. IMO.
got alot of extra money? this seems pretty obvious -- how about a pair of pultecs?
EDIT: I just thought of this.. has anyone ever tried running mixes thru a pair of mcintosh tube power amps? you'd have to pad the output a bit. I love that sound on SOME material. I can't imagine it making sterile techno sound worse.
mike p