It comes down to output quality, and most of the time, Analog > Digital [Analog offers better dynamic range, but digital gives a clearer signal]. Regardless, digital output on all cards should be the same [prior to any extra encoding that may be going on]
Auzentech <> ASUS > HT Omega > Creative
For under $100, the best options are:
ASUS Xonar Essence ST ~$50
ASUS Xonar D1/DX ~$89
HT Omega Striker ~$89
Above that, the Auzentech Forte, ASUS D2/DX, Auzentech Prelude, and ASUS Xonar Essence STX are the next batch of cards to recommend.
The Prelude is probably the best all around bet, although the Striker and D1/DX are very attractive options for a lower price.