I'm not a huge fan of the 63's myself though they do have a big following. They are less detailed than the 57s and kindof lifeless. I also find this true of later Quad designs. Some who have modified them (though I haven't heard and don't see how its possible given their design), claim their 63's are unsurpassed. The later Quads (through those being made today) are adaptations of the 63. I wish Quad had opted to perpetuate/evolve the 57. I believe the main reason for developing off the 63 was marketability and reliability (like the Martin Logans, they're louder, they have a larger sweet spot, less demanding on amps [though that's a bit overplayed in the community and less of an issue than many think -- with Quads that is], are more reliable etc.).
With regards to the loudness issue, powered by a five watt tube amp, my Quad 57's played as loud as I would ever need in a 10x15 room. When listening I sat practically on top of the speakers as I'm certain that is the best place to be. The treble transducer (positioned in the middle of the speaker and flanked by a bass transducer on either side) outputs sound from about 2/3rds the way up the panel (you can hear this if you put your ear close to the speaker). Conversely the bass outputs from the lower 1/4. It's very important when listening that your ears are in line with this point of output (the treble that is). People mention raising their Quads for this reason (and to reduce room resonance). I never did but developed a hunchback as a result of not doing so.
Edited by milezone - 4/20/12 at 12:01am