Hummel A Minor?
MASSIVELY HARD.
Mendy 1 is a standard first Romantic concerto, as are Grieg and Schumann. Mendy 2 in D minor is one I would choose over any of these three, though.
Either of the first two Beethoven concerti are good. No.3 is a bit harder, Nos. 4 and 5 should definitely be avoided for now.
Brahms? Are you guys kidding? The D minor, while not quite as difficult as the Bb major, is still a mature and fiendish work to be played by extremely advanced pianists. Hardly a concerto for someone coming out of something like Mozart.
There are a lot of good concerti besides the mainstream ones, but I don't know enough about their difficulty to tell you if they are good concerti for you to do.
Phil