For a stimulating workout of your brain, give Bach’s Concerto For 4 Harpsichords And Orchestra a listen. Each harpsichord plays a separate melody (the form of the Fugue, employing a lot of counterpoint), all following the chord progressions, modulations, etc. played by the orchestra. But it’s not just an intellectual challenge, it’s also a thrilling musical ride!
For the enlargement of your soul, listen to any of his Passions.
Believe me, I have listened to a lot of Bach’s music. I still own a fair amount of Bach recordings. Same goes with Mozart, Beethoven, Brahms, Handel, etc, etc, etc.
Bottom line, I am just not a fan of the "Common Practice" eras of classical music. Tonal classical music bores me tor the most part.
With regards to classical music, I only like: atonal, serial, avant-garde, 12 tone, and other forms of 20th and 21st century music. I only tend to like ’challenging’ and ’thorny’ sounding music. Most of my listening of classical music, is from post 1950’s, up through the present.
I have tried many times to listen to earlier eras of classical music, but it bores me. And I return to it from time to time, including Bach, in hopes that it will someday ’click’ with me. But despite honest attempts, no luck so far.