The speakers I own (Sforzando JL-1s), and other speakers designed by Fr. Richard Davidson (the old ITC speakers from way back, for example), would meet your requirements. You'd need me to get you in touch with him, though, as these speakers are not really commercially available or something you could listen to other than at a few people's homes. Generally I agree with the suggestions about omnis, and I have heard Avalons off-axis sound quite good, though I must say that they really can lock-in when you're in the right spot. One other more or less conventional speaker that I have heard and believe was not mentioned above that seems to do well from off axis is the von Schweikert VR4; I'd imagine that the entire VR line probably would be similar.