In general, the more efficient a speaker is the better will play at lower volumes. Consequently, horns will be the best choice. Since you can sit 10 feet away from the speakers Avantgarde UNO comes to my mind though might not have a too high WAF.
Another way to get good sound at low volumes is to use a subwoofer. This is because in IMO one will not be able to get a healthy bass al low volumes unless he/she goes for very expensive speakers (often not even then). Since you are not interested in getting bookshelf's speakers you should get some smaller floor standers with a subwoofer. (As Elizabeth commented above smaller speakers do generally play better than larger ones at low levels).
Another way to get good sound at low volumes is to use a subwoofer. This is because in IMO one will not be able to get a healthy bass al low volumes unless he/she goes for very expensive speakers (often not even then). Since you are not interested in getting bookshelf's speakers you should get some smaller floor standers with a subwoofer. (As Elizabeth commented above smaller speakers do generally play better than larger ones at low levels).