Cable Cords For Tv This Is A Great Hdmi Cable Just Bought A LCD Tv But The Quality Is Crappy, Is It Worth Buying A HDMI Cord?

Just bought a LCD tv but the quality is crappy, is it worth buying a HDMI cord? - cable cords for tv this is a great hdmi cable

I bought a RCA 40 "LCD HDTV 1080p. I have my Verizon and Cable Component HD channels look great, but digital channels are really poor. If I buy an HDMI cable instead of HDMI YPbPr noticeable difference in quality?

Thank you.