For regular cable TV have you tried using an external scaler like the IScan or the Viewsonic. Normal TV is definitely watcheable even on the X1 and a scaler.
All the lower pictures in my X1 are standard cable with a Viewsonic TV tuner.
http://www.spacelofts.com/x1/

Picture can be better because this is standard out of box colors without calibration.



http://www.quadloft.com/hometheater- new HT