Inherit all styles from base theme expect a few
As noted on the sub-theme page, a sub (or child) theme will inherit all the parent's css files "as long as you declare at least one stylesheet in your sub-theme's .info file". 

You can override a stylesheet simply by declaring one of the same name in your sub-theme's .info file. If there is a stylesheet you don't want in your sub-theme, just add an empty file with same name to the sub-theme's .info file.