CADMAX: Is there any reason that you should not run the TV in store mode?
There are a number of websites that offer "best configuration" for "X" TV - some are good, some are not. Google a couple of them and try them out for a day or two - 5 minutes is not going to be long enough! Settle for the one you like best.
As for the picture quality - sometimes it's down to the program. Some programs you watch are a bit wishy-washy, then you watch Hawaii 5-0 or CSI Miami and you see the WOW! factor. As the earlier poster said, make sure your MySkyHDi is configured correctly for full HD (1080i).
I agree with the comments on the cables. I got a 10m cable from Ascent for a friend - HN/DS/NL etc were a couple of hundred for half the length. Got one for around $50 online (not the cheapest by the way) and it works perfectly.