What piano music should I invest in?

I'm going to college, and I need to know what piano music I can get while I can still get it cheap from the local music store. I have WTC Book I, Complete Beethoven Sonatas, Complete Chopin Etudes and Scherzi, Liszt Concert Etudes, Schumann's Fantasiestueck, and all the Rachmaninoff Preludes, along with other random stuff. What would be a good investment before college?