1. If I use a Polarizer does that negate the need for a UV Filter?
2. If I use a Variable ND does that negate the need for a Polarizer?
3. Is there a negative effect from using several different types of filters let say a UV, Polarizer and Vari ND all at once or is there a net positive effect from using all 3?
4. What is the best pattern to organize the filters on the lens if using a variety of filter types. ie. Vari ND 1st, then Polarizer, then UV?
5. Is it best to buy the best SET of filters from the same brand or the best individual filters from different brands.
6. Is there some kind of rating system for Filters that can be used to compare their effectiveness? ie effect on sharpness, color etc. How would someone actually choose one filter from another to find the best one if there is no rating system? Is there a really reliable resource on the Web?

Sorry if there is some thread that covers this, but I haven't come across any that concisely address this topic.