Gaining a Wider Audience With Precision and Polish December 3, 2004 By Allan Kozinn  The Pacifica Quartet, which is celebrating its 10th anniversary this year, showed itself to be a magnificently polished ensemble on Wednesday evening, and if it isn't as well known as it should be, that may change soon.   In addition to a place on the Chamber Music of Lincoln Center's varsity roster -- called Chamber Music Society Two -- the quartet holds residencies at the University of Chicago and the University of Illinois at Urbana-Champaign, and it has recorded a handful of discs for the Chicago-based Cedille label.   The group opened the program at Alice Tully Hall with Mendelssohn's Quartet No. 2 in A minor (Op. 13), a sweetly youthful, richly hued piece that benefited both from the remarkable precision the players brought to it and from the gorup's use of vibrato, which was laid on thick enough to give the music a warm glow but was never overdone.   Those same qualities served the quartet reasonably well in Brahms's Piano Quintet in F minor (Op. 34a), for which they were joined by Gilbert Kalish. Here, though, the players' precision sometimes made the music sound more polite -- or less completely on the emotional edge -- than it should be. By the end of the long first movement, though, the musicians had loosened up considerably.   Between the Mendelssohn and Brahms works, the quartet captured the full measure of both eerieness and provocative humor in Gyorgy Ligeti's String Quartet No. 1, "Metamorphoses nocturnes" (1953-1954).