just bought a 40″ lcd sony bravia 720p and when i watch an hd dvd, the picture quality is perfect…but when i watch my regular cable programming through a digital box, the picture quality is grainy and worse than the sony crt tv that i am replacing….though i appreciate the high quality of dvd viewing, the price seems quite high considering that 70+ channels are now subpar….is this tv too good for the quality of signal that is available or is there another issue?..thanks