The efficiency is obtained with better magnets "motors", cabinet loading and design. The efficiency is not magic it is based on sound engineering. I have listened to the Silverline line only briefly, so I am not a good judge. I am very familiar with the Coincidents. The victory needs at least 300hrs, Mr blume says they need at least 400hrs before you can really listen to the speaker. I own the Total Victory, picture a Victory with four 8 inch woofers on the side and taller. I have listened to the Victory, it is a wonderfull speakers specially with tubes. I heard it with a 300b's, about 8 watts. I am sure they will sound good with a 2A3, but I think a little more power would be needed for a full orchestra at room filling levels.
In a smaller room and at lower volume levels it should suffice. This comes from someone who has no expirience with 2A3 amps. So take it with a grain of salt.
Good luck in your search.