[JFreak]

Once you get past threshold of good enough you cannot hear a difference. There are a lot of documented blind tests out there suggesting you should not worry so much about AD/DA quality unless you plan to use external hardware extensively. Another blind tests say a bad 192kHz converter sounds worse than a god 48kHz converter.

The preamps however, they are either "clean" or made to color the sound in some way. what is "good" for you depends on your priorities. There are many colours available, and some aim for absolutely clear representation of the signal. I myself usually use Focusrite ISA preamps which are on the clean side, being characterised as "neutral" but still have something that says they are worth their price.

As in everything, the closer to the source you go you get bigger gains. Make a better song, find a better artist, have a better day for recording, use a better mic... never worry about the quality of the mic cable so long as it is good enough.