The title is likely a nod to the song "The End" from the Beatles' "Abbey Road" album (1970). The short song contains the lyrics "And in the end, the love you take, is equal to the love you make."
In this episode it's revealed that Frasier has a whole utility closet devoted to hats. At no point in the series Is he seen wearing one.
Frasier and Cam's apartments floor plan and layout are identical.
It's no coincidence that Cam's apartment number is 2001, likely as a tribute to producer David Angell, who was killed in the 9/11 terrorist attacks. Although the more likely explanation is simply that since Frasier's apartment number being 1901 and since Cam's apartment has been established as being directly above Frasier's, it makes sense that the two apartment numbers share the same last two digits, with the first two digits indicating the floor number.
With Niles being involved more and more with Daphne, the truce and formalized friendship between Cam and Frasier would have been a great opportunity for Frasier to enjoy the companionship of another cultured friend.