When viewing HDTV on some local channels, they only come in 4:3 standard letterbox ratio leaving bars on the sides of the screen. If I don't want to zoom or stretch the picture and with burn-in always a concern, what is the best (coolest) color to leave the bars to help avoid the burn-in problem? Black, gray, white, don't do it at all - what? Thanks in advance for any help/ideas!