Scot:
Due to the vague terminology vendors use, not sure what is meant, exactly, by pixel multiplier. Could mean a doubler or some algorithm that fills in the spaces between scan lines or ? It may work with a doubler, may not. A doubler doesn't actually double the number of lines, it just takes the two scans and paints them as one progressive scan. The result is still same number of lines, but little or no space between, depending on the brand and method of laying them together. Thats the difference between the $10,000 and $3,000 ones. Some sets will show this difference, others won't, therfore, it gets back to the the $64 question, is your set capable of showing it? Thats why I suggested a demo or used one from a reputable source. Better still, if you could "test drive" one before buying on your set. Like most manufacturers, the sets come out of the box in wide varying states of tune. How much yours would need will only really be known when you try to tweak it. You could put on a test dvd, and it might show you are really close, but when the tech goes to tweak it, there may be no adjustment possible or be at its max range/limit. One thing is for sure, it will show what your set will do at it's best and if there are any fixable defects. Best done while it's in warranty, too! Price? Each area is going to have different labor rates. Could be $50 to $100/hr, but might only take one or two hours. Again, every set is unique. I have seen some respond well, others just a little, but all look better to some degree. The builders just don't have the time to max 'em out.
Bottom line, you have a set that can look great, and will give you some great dvd performance if the above mentioned is tried/applied. Just depends on how fast (read $$$ spent) you want to go!