I have an Aluminum Trek 820 (1999 I believe) with a Manitou Pro front fork and i want to try to reduce the weight of the bike. I don't really want to get a new bike, I would rather upgrade the one that I have. will new front/rear derailleurs, crankset, shift/brake levers, cassette make any real diffrence in the weight or is it just a waste of money? If it is not worth it, are there any opinions on a new bike in 500-800 range? I would be looking for something pretty much just like my 820 but lighter and with better components. Any ideas?