Hi DarKWind,
If you want to strengthen your left hand, play pieces incorporating the left hand Eg. Liszt's Ballade No.2 or Chopin's Revolutionary Etude (Op.10 No.12). A great piece to learn how to repeatnotes evenly, quickly, and lightly, I recommend Liszt's Tarantella. I just finished it and now I can play repeated notes much more comfortably.
Hi PeterHK
You own a PLEYEL P124 upright. I used to have an upright, but replaced it with a grand because the Upright couldn't repeat notes very quickly or evenly. You play a lot of liszt. How can you play Liszt's music, which often requires repeated notes? If you found a way of playing repeated notes quickly and well on an upright, you should write a book or something about it.
donjuan