You may be better off posting on the forums for those specific games. There may be a known issue.
Your motherboard manufacturer may have updated drivers for your sound hardware, or there may be updated versions of the games that fix this issue.
Personally I use a Creative Labs Audigy 2 ZS. These are available OEM from click here for about 60quid, if you don't mind getting the card unboxed and with no instructions then this might be for you. It does come with a driver CD, and is very easy to set up.