The Pass is a fine amp for the Quatro's. I personally like the Ayre Ref amp better as there is a ton of synergy, but that's me.
I own the same integrated, AX5/TWenty, and it will sound a spec better after about 15 minutes or so, but I won't leave it on all the time. If you don't have over 400 hours on that input (each input must be broken in separately and you want to really beak each input in using the listening volume level that you use normally), then it may also be part of breaking in. I know that the time of sounding it's best shorted considerably once I was all broken in. Once I get it back from Ayre with the Vandersteen cross over installed, I'm sure I'll need to run them for many hours to break them in too, but since I need to break in the new Quatro's, it's not a big deal, lol.
I personally hate the break in time. I'd rather just do a plug and play from day one. Guess we'd have to pay for the hours of break in at the factory. I know Vandersteen does a pretty good job of breaking in that midrange before assembly, but you still need to break in the rest of the speaker once you get it just like anything else. With the newer and stiff components used and all the silver in the amps/electronics, it takes so much longer than it ever did.
