Alex, in the December issue Consumer Reports has their latest TV tests. The top-rated plasma in his price range would be the Panasonic TC-P46S30, which, for example is available from Amazon for $727 with no tax and free shipping.

As to improved sound, I don't really like the idea of an intermediate step such as a sound bar, as compared with a relatively simple setup with an inexpensive receiver and small separate speakers.

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Enjoy the music, not the equipment.