Is it necessary to use HDMI 1.3 cables to connect 1.3 devices to 1.3 compliant HDTV or would using an earlier version of the cable prevent receipt of best possible picture and sound?

It is not necessary to use HDMI 1.3 cables to connect 1.3 devices to a 1.3 compliant HDTV; earlier versions of HDMI cables (like HDMI 1.2) can still work. However, using older cables may limit the performance and prevent the receipt of the best possible picture and sound quality, especially if you're utilizing features like higher resolutions or deep color that HDMI 1.3 supports. For optimal performance, especially with advanced features, it's recommended to use HDMI 1.3 or higher cables.