HT Omega, Auzentech, and ASUS lead the pack. [Note that ASUS/HT Omega use the same chipset, so its features more then anything between them].
At the sub $100 range, ASUS and HT Omega lead the pack:
ASUS Xonar DS [Lacks DDL encoding]
ASUS Xonar D1/DX [Lacks DTS-Connect encoding]
HT Omega Striker
Moving up a bit, you start to see Auzentechs offerings:
Auzentech Forte
Auzentech Prelude
ASUS Xonar D2/D2X
ASUS Essence STX
HT Omega Claro
To me, no other card is even worth considering, unless you need HDMI in/outputs or a HT card, where the ASUS HDAV 1.3 and Auzentech HT HD are top tier options.