I've just gone through testing several 2 meter cables. I was using Monoprice $3 cables on my top line Panny plasma, which seemed good. I switched to Wireworld Starlight 6 and there was a definite improvement, but nothing I would call huge. Colors are more saturated, and edges of objects were a little bit smoother, more "film" like. Streaming Netflix audio to my NAD M51 DAC using the WW HDMI cable did offer a small increase in sound quality, similar to going from a good $100 IC to, say, a good $200 IC. Still not huge, but noticeable.
At about $200 each retail, I would not say the improvement from the WW HDMIs would be worth it to me (and I'm an audiophile, not a videophile, but used to shelling out $500 for ICs), but I bought them used at a very large discount.
I also tried Apollo AV "Lightning" a $50 list cable that is on closeout for around $15. It was also better than the Monoprice, and very close to the Wireworld. I recommend them highly for the price. If you want to try a better HDMI to see if you get results, this is a good safe one to try for the $.
http://www.apolloa-v.com/75-off-original-retail-apollo-av-lightning-hdmi-silver-plated-ofc-v1-4-high-speed-with-ethernet/