Can't comment on the NAD T777. NAD equipment has evolved to include more digital equipment than analog. That said.......
I use a Nad C375BEE integrated for music only. Auditioned MANY bookshelf speakers and found that the clear winner was the PSB Imagine B. Probably because NAD and PSB are/were sister companies. I have never been able to find a good pair of PSB Synchrony 1B speakers since they have been out of production for several years but they are regarded as the superior PSB bookshelf.
If you want to change to a different amp then that starts a new search. If possible, try to audition your amp with PSB speakers. There may be other brands that sound better with NAD equipment but I haven't found them.
I use a Nad C375BEE integrated for music only. Auditioned MANY bookshelf speakers and found that the clear winner was the PSB Imagine B. Probably because NAD and PSB are/were sister companies. I have never been able to find a good pair of PSB Synchrony 1B speakers since they have been out of production for several years but they are regarded as the superior PSB bookshelf.
If you want to change to a different amp then that starts a new search. If possible, try to audition your amp with PSB speakers. There may be other brands that sound better with NAD equipment but I haven't found them.