There are several string quartets that stand out from the crowd, with the Emerson String Quartet, and Quatuor Mosaiques being among my favorites. I'm not sure if either of these groups have recorded the Mozart work you mention, but it's worth listening. The Quatuor Mosaiques, by the way, have several wonderful recordings on the Astree label of Mozart and Haydn, featuring fine performances and terrific audio quality.
