Actually, right at this precise moment I am listening to Ernő Dohnányi's first Piano Quintet.
It is a marvellous, sadly underperformed work. There is a fantastic recording of it on YouTube.
I have had a late obsession with piano quintets, I must admit.
At the moment I would say the greatest three piano quintets ever written are those of Johannes Brahms, César Franck, and Dohnányi's No. 1.
Give them a listen.
"There's nothing remarkable about it. All one has to do is hit the right notes at the right time and the instrument plays itself." - J.S. Bach