UV filters "for protection" are largely a waste of money. A lens hood or a lens cap does a far better job protecting a lens, than some thin piece of glass every could.

Still, personally I have UV filters (B+W 010 MRC) for all my lenses that can be fitted with filters. I'm in the "third camp". I have em, but only use "protection" when it actually might serve a purpose. So the UV's are stored in my camera bag until needed... such as shooting out in a sandstorm. That's about 1% of the time. So I'd recommend you make UV filter low priority, unless you plan to shoot paintball contests, sand storms, etc. Get and use the lens hood for all your lenses instead, if you don't already have them.

A quality C-Pol is a much more useful filter for digital photography. They're especially handy to have for scenic shots, portraits, anywhere there are reflections you need to control, and some other purposes. Many of the effects of C-Pols are difficult or impossible to replicate in post-processing software... Unlike most other filters which are very easily emulated or even out-done by software, when shooting digital.

You may not need a C-Pol for some of your lenses. I tend to use them most on wide angle through short telephoto focal lengths... less often or even rarely on longer telephotos.

The best bang for your buck are B+W Kaesemann HT (High Transmissive) filters. At their quality level, B+W are actually among the lower priced... Compare at B&H Photo or Adorama and you'll find you can easily spend 50% to 100% more to get the same or lesser quality.

I don't know anything about Promaster filters. As others have said, they are probably made by someone else and re-labelled. Hoya/Kenko make a lot of filters that are sold under other brand names.

Whatever you buy, look closely at the specs because most manufacturers make several different grades that sell at different prices. Hoya probably has the most grades.... five or six different C-Pol. Even more if you consider that Kenko filters are made by the same company as Hoya.

For that matter, B+W offers four grades....

- Their least expensive B+W "SC" are single-coated Schott glass in brass frame with standard polarizing foils.
- B+W "MRC" are a step up with 8-layer multi-coatings, Schott glass in brass frames.
- B+W Kaesemann F-Pro HT MRC are another step up, same as above but "high transmissive" with finer polarizing foils, edge-sealed for moisture resistance.
- B+W Kaesemann XS-Pro HT Nano MRC are their top-of-the line, same as above but using 16-layer multi-coatings and a "slimmer" frame.