One opportunity could be the 2pi Towers - they combine reasonable size (46" X 16" X 13" - meaning they are large compared to many 'normal' hifi speakers, but on the small side compared to many other Pi speakers) with a wide frequency range & a very reasonable price ($108.62 a pair). There's also the normal 2pi's - cost the same, measures 22" X 15" X 10". They haven't got the same deep bass as the Towers, though.

Lots of other possibilities - maybe someone else have suggestions.