Svideo is not digital. Nor can it transmit HD material, so many skip it with an HDTV from their HD cable/sat box. Shouldn't be any issue with doing this.

Digital sat is only CAPABLE of 480 lines of resolution. But resolution is not the end-all factor in picture quality. DirecTV tends to compress the channels so much it doesn't matter what the resolution is, they still look bad on an HDTV. Soft and occasionally macro-blocking is visible. I see this on a 20" TV, on my big screen it is not worth watching. I don't think Dish is as bad right now, but that is from what others tell me so I can't really say.