As a confirmed Mozartian, my perspective may not be the best, but
I'm surprised that Sinfonia Concertante would be a difficult piece to
warm up to.  I've always thought of it as one of his most immediately
attractive--the opening is kind of bland, but afterwards there's a
succession of beautiful melodies.  The second movement is not only
beautiful, but has an intensity of emotion bordering on the Romantic.
But it can be a tricky work in performance: you need soloists with a
lot of spirit who have the discipline not to go over the top. The Szell
recording has a high reputation, but the tempi in the outer movements
are a bit too fast for me.  The one I like the best is an old Vanguard
recording with Josef Suk as one of the soloists, also conducting his
own chamber orchestra.  It's a very straightforward classicist reading,
but gets all the emotional nuances right.  If you like old-fashioned
romantic-style Mozart, I'd go for the Perlman/Zuckerman/Mehta recording
on DGG--it's a live performance, very exciting, lots of virtuoso spirit.
I don't know the Heifetz/Primrose version; I guess that's just one more
thing to listen to...

Peter Goldstein