What is it you're looking for? Better sound quality? What are you connecting it to and are you using digital or analogue? If you're using analogue you may well not notice any difference with a better card. Also assuming you want to avoid creative... Anyway:
I did a lot of research for my card and came up with the Asus Xonar D2/PM
which has a better SNR than your current card (118 db vs 107db for the DS). THD may be better too. It can also do Dolby in addition to DTS. Comes with a MIDI port daughter card and bundled basic music production software if that's your bag. I've linked to the PCI version: there's a pci-e version, but be aware that the pci-e one needs power from a floppy connector, unlike the PCI which needs no additional power.
If you can stretch to £140 there's the Asus Xonar Essence ST
which is the next step in sound quality (124db SNR) Can only do stereo, unless you buy the expansion card. I've linked to the PCI version; again there's a pci-e version with the same caveat as above.
Hope this helps.