I have owned all of these TV's at some point over the last year. For sheer picture quality the F4500 is the winner by some distance...in a dark room. It has a very reflective screen. Blu rays on this TV look absolutely fantastic. Motion is smooth and contrast ratio is highest on the list. Transformers Dark of the Moon and Life of Pi made my jaw hit the floor.
Very good review of the F4500 Vs. X60 here;
The F5000 has better colour saturation than the E6 but the E6 scores higher for image processing. Blu rays on the E6 are better than F5000 but normal viewing better on F5000. The F5000 also has a more uniform backlight.
For SD viewing the 40" F5000 is the best.
For gaming the F4500. Great colours/contrast and hardly any blur at all.
If you watch mostly HD then I would recommend the 46" F5000. Step up in size is hugely enjoyable! If you can control the lighting in your room and watch TV mostly in the evening then the F4500.
Horses for courses!