An aside: waiting for 'breaking in': if the sound is not basically 90% or more there straight up, it's NOT going to magically arrive with breaking in.
It IS true some benefit from use arrives after a bit of time, and the many gushing: "at first it sucked, but after 100 hours it became perfect.." are typical audiophile nervosia exaggerations. If it sucked to start, it STILL is gonna suck afer breaking in, anything else is dealer bull#hit to stick you with something you do not really want.
The sound upon arrival should be really good, then with 'break in' it can become fantastic.
Somehow "breaking in" has become the magic bullet cure all phrase to stall the instantanious reaization that it is crap and you know it, and want to return it immediately.
I KNOW this is going to bring out a dozen stories how "I didn't believe, BUT..." but those mask the ten times greater stories "I got screwed because I waited... hoping.. and finally gave up.. sold it a year later and got what i wanted"
Waiting and hoping for a miracle is only benefiting the dealer. If it isn't right in your place, take it back.
(If you can't take it back, perhaps this diatribe will benefit others in similar situations)
IMO.