I wud say go fot it... reason:
1. huge difference when u listen into headphones/earphones
2. Improve the Source before upgrading the peripheral (speaker set)
hence ur wish as per ur budget. but incase u do care about sound quality, i recommend following upgrade path:
Creative Audigy Value - 1.5k
Speaker upgrade to Altec Lansing VS4121 (2.1 setup) ~ 1.5k or Logitech X-530 (5.1 setup) ~ 4k
Result: A new high in terms of sound quality level for your Audio setup.