HDMI cable made a difference in picture quality??


I just bought an a 42 inch LG LCD flat screen TV which is has full HD function. I have a HD cable box and opted to use RCA cables betwwen the box and TV. I am getting missed opinions from the cable provider and the LG dealer about the usefulness of the HDMI cable hookup. Does it actually improve picture quality??? If so,how much? and will it also improve non-HD programming??? I have seen several adds from Monster Cable and Audioquest touting their HDMI cables. Monster has one that is about $70; another is about $100. I have seen even higher price tags from Audioquest. All comments welcomed. Thanks Jim
sunnyjim
The power conditioner to TV and cable box will make a difference. I would also upgrade the power cords for both the TV and the cable box. PS Audio makes a nice power cable for the small connector often used in video and not too expensive. HDMI the way to go for facility and upscaling SD but, I don't think there should be much of a difference in HD with very good component cables (the ones that come with a cable box are usually not too good) and HDMI.
Below is a copy of what I posted here on 8/20/2009 http://forum.audiogon.com/cgi-bin/fr.pl?fcabl&1250622275&openmine&zzNasaman&4&5#Nasaman

- Nordost Silver Screen: 8 (very bright, clean and details. Low noise). Highly recommend for High-end users.

- AQ hdmi-3:............ 8 (very deep, beautiful, and accurate colors. Great details & very low noise). Highly recommend for hi-end users.

- AQ hdmi-1:............ 7.5 (colorful, details, and low noise) Recommend for Hi-end users.

- Supra Cable v1.3:..... 7 (bright, clean, & details. Low noise & decent price). Good for Hi-end users.

- BlueJeanCable:........ 5 (decent colors, somewhat noisy & lack of sharpness. Great price.) Decent for Hi-end users.

- Monster-1000:......... 4.5 (its video quality is, somewhat, equally to BJC)I wouldn't buy it.

- MonoPrice:............ 2 (very dark, nasty, & inaccurate colors. Lots of video noise; it's a VCR's picture quality) Not recommend for Hi-end users.
The Wegrzyn's pure 4N solid silver HDMI cable is the best HDMI cable that I have ever tried. You can see fine details in the HD picture that were missing with other HDMI cables that I have compared them with!..
Once again, I have seen no noticable difference in HDMI cable output with the different cables I have tried.

It could be those seeing a difference are using some of those "Magic" power cables too, that "open up the soundstage, and reveal the inner detail".

Once again, spend your money on components that make an improvement in sound/picture, not on crazy cables.