As the left channel of my old Receiver (a Yamaha RX-V392RDS) doesn't work any longer (and I don't need a tuner), I'm currently searching for a new amplifier. It will be used almost exclusively to listen to music from my Computer (which has some version of the sblive built in)

..and here come the questions ..

1) Would I get better sound, if I'd buy an amplifier with a digital in (assuming, it is possible to get a digital signal out of the sblive ...) ?
2) Would it bring any advantage to have an amp with Dolby-Digital or something ? (just to listen to music ...?)
3) If the answer to the first is yes and to the second no: Are there any stereo-amps with digital-in out there ? (haven't found one, yet)

Please forgive me if I am wrong about anything as I am no expert in the subject, but I'll do my best.

1. Better sound? Possibly, but any improvement also might not be noticeable. A digital in will ensure that any noise from the soundcard does not make it to the amp, also it’s likely that the DAC in an amp is far better than the one in your soundcard, but again this may or may not be a noticeable difference.

2. Dolby D or even DTS? Probably not. If you only are looking at a two channel amp, you would probably have little use for Dolby or DTS encoded sounds. You can buy music that is encoded in these formats but if you do not have a 5/6/7.1 setup, they probably would not be something you would buy. If you are looking to just listen to music it’s most likely you will be using PCM only.

3. Don’t know of any but I couldn’t confirm they don’t exist anywhere. Again, digital is used mostly in mainstream applications for multi-channel sound.

Some good options:
Exclusive computer use: Griffin Powerwave
A step up: sound card (Chaintech av710, EMU 0404)+TEAC A-L700P
General use: sound card + vintage stereo amp (lots of options) or Panasonic SA-XR series receiver

I'd say go with the powerwave for now. Should be much better than your current gear. Unless you need more power.

There are certainly recievers and pre-amps with digital in. I don't know about integrated amplifiers, but haven't looked.

Dolby digital/DTS is useful for music if you have music in those formats. Most common woud be a music DVD, but there are DTS CD's also. A Dolby digital decoder would also give you bass management (translation: a built in subwoofer crossover) which you could use with 2 channel music.