In what way is the PQ poor? And is this on any specific channels?
If you're watching SD channels on a larger screen, then a 576i source picture is being upscaled to 1080i and then onwards to 2160. That's never going to work brilliantly, but you may be able to experiment with whether your V6 or TV does the upscaling.
On your V6, follow Home > Help & Settings > Settings > Video output. If 2160 is selected, then your V6 will be doing all the upscaling. It'll be worth experimenting with disabling that, and forcing your V6 to output at 1080 - your TV then does the 1080>2160 bit.
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