I looked up the power consumption of CRT vs. LCD TV's. Turns out for small screen sizes (around 30 inches), the difference isn't very big.
If your CRT TV is similar to the Toshiba 30HF83 (about the same weight as yours) it uses about 150 watts of electricity when in use, according to its manual. A new LED TV such as the Samsung UN32H5500 uses about 27 watts. Assuming 2000 hours of usage a year (about 6 hours a day) and 10 cents/kwh electricity cost, the LCD would save you only about $25/year on electricity. So that would be about 20 years for the $500 LCD to pay for itself.
Take it a step further, and say you invested that $500 at only 3% interest, and that $500 would earn about another $400 over 20 years. Not to mention that the LCD almost certainly wouldn't last 20 years, but the CRT might. I would say that if you are happy with the picture quality, then you got a pretty sweet deal. If electricity costs go up significantly, that would alter the calculus a bit. But as longs as they keep making devices with component outputs, I would say you're golden.