If you like the proac sound but wish to improve soundstage & frequency response, ATC is an obvious contender, a 20, 40 or used 50.
Generally, of the ones you mention, the bigger Spendors & Harbeths (30 etc) offer a more complete sound in a similar style, i.e. better frequency response.
Generally, of the ones you mention, the bigger Spendors & Harbeths (30 etc) offer a more complete sound in a similar style, i.e. better frequency response.