It's a personal choice. Most members here will use the black/gray bars on the side to preserve original aspect ratio, rather that distort a 4:3 image.
All 16:9 sets (and most, if not all HDTV stb's) have some kind of stretch/zoom mode for 4:3 material. But if the broadcaster is upconverting 4:3 material to HDTV, only the Dish 6000 will give you control over that. The DTC-100 has a workaround, too, but it's less elegant (more buttons to push), other stb's may also do this.
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