Speaker should be upgraded with sound card ? Help Me !!

Ok, here is my case. I'm using JBL Creature II with onboard sound card, and they work fine.
But, I'm wondering to replace either one of both to improve my sound quality.
What should I do with limited budget which is around $60-$70 ?
Should I buy Audigy ZS or sell my current speaker to buy a better one ?
I would appreciate your suggestions.

I doubt you would hear the difference with a new soundcard with those speakers.
Save the money for a better speaker set.

I also suggest saving up for a truly good set of speakers. Recently I upgraded from a ~100w set of altec lansings that I thought sounded good to the logitech Z-5500's. After I ordered I started having second thoughts, but WOW what a difference. It makes my old speakers(which are probably better than yours) sound like they are underwater, even with onboard sound. I got an audigy 1 for free and modded it to an audigy 2 but that didn't make nearly as much difference as a nice set of speakers.