For years, before LP's, #20 was known as "the" Mozart piano concerto. Many thought he had written no others. It's a bit different from his other 26 piano concertos, the vehemence almost Beethovenian in the first movement. I've tended to see it as a warmup for the Requiem.
Brahms: Piano Concerto #2 in B-flat, Op. 83
The first concerto was something of a musical shipwreck and took a while to work its way into the repertory. The second is a masterpiece. However, its construction is a bit unusual. It's cast in 4 movements, rather than the traditional 3. Clara Schumann referred to it, tongue-in-cheek, as a "symphony for piano". The finale looks backward to Mozart, specifically to the #27 concerto.
Brahms: Piano Quintet in F minor, Op. 34
A magnificent chamber work for piano, 2 violins, viola and cello, although the piano tends to dominate. It's an undisputed masterpiece, and I enjoy listening to it and following along with the score. The second movement is rhythmically tricky, and I have to count "one-and-two-and-three-and-" or else I get lost.
Beethoven: Symphony #7 in A, Op. 92
I prefer #9, but #7 is my second favorite. Roger Norrington's recording observes Beethoven's metronome markings, and the finale is absolutely hair-raising. At the posted speed, incidentally, the second movement is not a dirge; in fact, it's not really slow at all.
Mussorgsky: Boris Godunov
The woman is hard core. Russian opera doesn't travel well, and there are a lot of operas I'd rather listen to. She's one serious lady.