I don't know about the other cards you mentioned, but the SoundBlaster Live Value most certainly does *NOT* have Dolby Digital decoding. I think it's a fair bet that the Santa Cruz doesn't, either. However, if you buy any of the SoundBlaster Live 5.1 series of cards (the SBLive mp3+ 5.1, the SBLive X-Gamer 5.1, etc.), those DO have Dolby Digital decoding built in.
Although, I've got to tell you, I don't recommend getting Dolby Digital decoding built into the sound card. It's better to get speakers with Dolby Digital decoding built in instead, because then the sound card (or DVD card, or whatever) can send the raw signal to the speakers to decode. The speakers do the decoding work rather than making the computer do it, and chances are, if you're watching something with Dolby Digital sound, you'll want to take as much of a burden off the computer as possible.