Leighton is my cadillac choice among fine art sellers. They consistently have a varied but quality assortment of artists and art styles, although their mainstays are European Impressionist and pre-Impressionist (and earlier -European Classic) paintings. You can expect a bit of competition; I've not 'stolen' a work from their auction selections - but that's a sign that they are purveyors of good product and have earned standing among loyal collectors seeking quality. Oh, every once in a while they have a 'reparation project' painting which is keen to check out whether you are in that buying niche or not; art lessons abound in these (ie. the 'sausage making' is often revealed!)