Well any sound card with SPDIF can pass through DTS from a DVD/Blu-ray, to an external decoder. If you are wanting to use DTS and 5.1 sound for gaming, then you would need a sound card that is capable of real time 5.1 DTS encoding. Xonar DS, is the cheapest card capable of that.
Oh yes, my mistake, wasn't paying attention!
X-Fi Titanium, would be the cheapest then that offers DTS real time encoding. Cheapest PCI-E Xonar that does, would be the D2/D2X. D1/DX is Dolby only.
It has the same type of socket as the Essence. Which is a coaxial socket, but can take a mini toslink cable, or normal toslike via an adaptor. My Essence came with one, so the D2/D2X would as well.