I recently auditioned the LS28 and Ref 5SE at a dealer. All else (Wilson Sasha DAW, kimber cables, arc ref250 amps, Linn akurate source, room position) remaining unchanged - the ref5SE offered a marginal improvement in presence, weight and sound stage over the Ls28. Tonality was virtually indistinguishable. Slightly better bass with 5SE. I cant numerically quantify the improvement - but i'd say it falls under the diminishing returns category. If it takes a spectacular system to reveal the marginal difference - i cant imaging how in an average users system the 5SE would outshine the LS28. That was my objective take - YMMV