Regarding soundcard recording quality, I invite you to listen to some recordings I have made with my Turtle Beach Santa Cruz card from various sources.
Absolute peak usually rests above -1 but is never clipped, and the noise floor is sitting down below -95db. There is no sample offset and sound quality is superb. Excellent for a card I bought for less than $100.00
If you are serious about doing audio mastering on PC, there are professional level sound cards available. They are expensive.
To clear up any questions on my authority, I have done freelance sound engineering for years in the broadcast and live performance fields.