"Stardust," Willie Nelson. Columbia. This 10-song collection of pop standards--from "Blue Skies" and "September Song" to "Someone to Watch Over Me"--isn't the CD you'd turn to if you were trying to show off the dynamics and range of your sound system. If, however, you're in the mood for classy, nostalgia-edged romanticism, Nelson's caressing vocals and Booker T. Jones' smooth arrangements contribute to an ideal package. The CD purity brings added intimacy to what was already an unusually warm, endearing album.