Replacing Power Cord On Flat Screen TV

Recently when repainting our family room I noticed that our Sony XRB TV had a replaceable power cord, so I connected an extra high end power cord to it to see what would happen. The cable that was included with the TV was surprisingly wimpy. To be honest I didn't really notice an improvement, but I'm not sure how to determine if improvements happened or not. Have any of you upgraded this cable on your high end TV and noticed improvements? If so, what should I be looking for to determine if it helped or not?

One thing I notice between playing Blu-Ray discs vs. a standard DVD in my upsampling DVD player is the clarity in the dark shadows of dark sections of movies. You can really notice the blotchiness of the transitions between dark and darker on the DVD vs the Blu-Ray. I've always attributed this to the quality of the media rather than any kind of power related issues, and in this example it is clearly demonstrated. Are there other things that clearly demonstrate the differences between power cables on hi-def TVs or am I just wasting time and money even bothering?

For reference, I am using a Monster Power Center to run my TV and other components through. I know Monster stuff is not true high end but I am not interested in buying a Shunyata or Richard Grey's unit for this purpose as I prefer to prioritize my audio system over video.
Look for better resolution or tighter focus. Better color saturation and vividness to the picture like removing a veil. Sound may improve as well with better extension and incresased clarity. Brightness and black level will also improve. Shielded cables will eliminate emi/rfi which can cause the images to be unstable/distorted. Replace it if possible.
What Tom6897 says.
Yeah agree. Adding an aftermarket powercable to my Sony Plasma really did improve grain and color.
(The Sony was a $5,000 42" Plasma back when they cost a lot...apologetics for those thinking: Sony? Plasma?)
Thanks for the responses. My TV looks darn good now, but I can't say it looks noticeably better. I'll do some more comparing and report back.
I kept my TV's powercord, since it seemed to be a reasonable gauge, but I did add a 10A Felix power conditioner in front of it. Now that was an immediate and obvious improvement at a very low cost.

You can find more about the DIY Felix over at Audio Circle.
With my Samsung 46" LCD TV I changed the stock 16 AWG power cord to the older Belden 17604 Power Cord. Since the cable was long enough I also plugged it into my Tice PowerBlock. This really yielded the biggest result. I echo some of the findings Tom6987 found.

I saw the better resolution, better color saturation and vividness to the picture. The one bad thing is that it showed how cruddy my cable tv source is. The 720P/1080I shows except sports looked more pixellated now matter how I calibrated the TV.
Yes Sir a Tice enhancer, Monster 3500 conditioner and 10ga shielded powercords have transformed our picture.
My audio system was down for a spell, so, for kicks, I took the Audio Magic Stealth XXX conditioner and the Electraglide Fat Boy PC and threw them on my Pioneer Elite Kuro 151FD plasma... and now I can't stand to take them off!!!