The TX-40DX653 has a maximum display resolution of 4K Ultra HD. That's over four times the display resolution of the most frequently found HD type of Full HD. 4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
This TV's display resolution (4K Ultra HD) is in fact the best display resolution across all comparable spec TVs that have been on the market for a similar time to the TX-40DX653.
Across similar types of TV the worst display resolution is HD Ready.
4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
It may also be worth considering one of the other 4K Ultra HD TVs currently available including because of it's better review score, the LG 49UH610 (£499.00).