I saw somewhere on the internet that Becker & Fagan used Magneplanar III speakers--not bookshelf--to master their recordings back in the day. The IIIa Maggies I used to own had a wonderfully realistic midrange, but were light on low bass. So mastering with them could have yielded pretty robust bass, although it never sounded excessive to me on any of their LPs, even on speakers with robust bass.
My ABC LP has the etching AB-1006 (RE-3). Does the "RE-3" signify a later reissue or pressing? It does sound very good.