6070's are extremely rare (new). Given that a 6020 will cost at least $3,000, $2300 is not a bad price.
Anyway, I discovered that the real culprit in my poor SD PQ is not the Panasonic TV, it is the hideous PQ that Charter is supplying. My cable box puts out 480p on non-HD, that is SD, channels and 1080i on HD. As an experiment, I set the output on my Netflix-enabled Blu-Ray player to 480 p and fed the signal into the same HDMI port that is used by the Charter cable box. Then I had Netflix stream episodes of the old Rockford Files and Adam 12 TV shows to the TV. The PQ was not HD, of course, but it was FAR above the level of SD out of the cable box. The picture was soft, but there were no processing/compression artifacts. I then carefully looked at the cable box Sd picture when fed into our other two flat panels, 50" Pioneer and 22" Dynex. In both cases the same poor PQ and artifacts were in evidence, just not as obvious because of the smaller screen size.
I had a Charter service guy come out and he agreed the SD PQ sucked, but there was nothing he could do about it. Even tried a box swap. No benefit. It is amazing that Netflix at $9 a month can supply better SD PQ than Charter does at 8x that.
Time to try an alternative.