Obviously, you have a couple of options. Before you get rid of your 2.5's, you should be sure its the right move. If you make a mistake, it will most likely be difficult to get another pair. I can tell you from first hand experiance that either an ARC VT-100, or a pair of Quicksilver V-4's, will breath new life into your system.
If you decide to go with new speakers, its a more difficult choice. Speakers like Zu and Tannoy don't have the same type of universal appeal of your ProAc's. Set them up right and the 2.5's can make just about anyone happy. Of the new speakers you list, Living Voice is probably the safest choice. I would also add DeVore. His customers are some of the most loyal in the industry. He makes both standard efficiency speakers, like your ProAc's, and has a high effifiency line as well.
If you decide to go with new speakers, its a more difficult choice. Speakers like Zu and Tannoy don't have the same type of universal appeal of your ProAc's. Set them up right and the 2.5's can make just about anyone happy. Of the new speakers you list, Living Voice is probably the safest choice. I would also add DeVore. His customers are some of the most loyal in the industry. He makes both standard efficiency speakers, like your ProAc's, and has a high effifiency line as well.