I own a 2001 Giant NRS 3 and the drivetrain(cassette, crank, and chain) is getting old and worn out. I was wondering what company i should go with for the drivetrain. I'm debating between Shimano, Race Face or Sram. I just put new shimano xt 9 speed shifters and shimano xt front derrailler. I do mountain bike races and I'm starting to do some more competitive and challenging stuff, if that will influence your opinion. I also don't want to overspend.