I own the 3.6, and have listened extensively to the 63's. Both are great. The quads are very easy to listen to and are very engaging, but you do lack dynamics and I think they need a big room. They are also rolled off in the highs. The best I heard was a double stacked version with a ribbon tweeter to extend the highs and a pair of subs. They require a lot of expertise to get right, but once done there's not much out there that will sound more pleasing. The Maggies have more sparkle and air and are much easier to set up provided you have high quality upstream components, and they do require a minimum of 100wpc with plenty of reserve power. Overall, they are far less expensive.
Magnepan vs Quad
I have owned and listened to the Maggie 3.5s for 2 1/2 years now. I have enjoyed them very much but I am now looking to upgrade my entire system. I am looking into the Quad 989s. Anyone out there compared the Maggies and the Quads? There isn't a Quad dealer even remotely close to me so I need some opinions. Thanks in advance for any suggestions.