many people here recommend the REL subs and they are also carried by Sumiko the importer for S.F. Getting a sub to work well with a monitor type speaker is daunting however, as in my experience, the x-over frequency needs to be relatively high to match up with the main speakers' high roll off of the bass. High crossover frequency means more phase problems and room interaction compared with a lower possible x-o that mating a sub to a full range floor stander allows.
