I have used the Cokin system for a while now, and it has definite pros and cons.

On the pro side, it is VERY good for use of split neutral density filters. Unlike a screw-on filter, you can slide a ND filter up or down and rotate the holder left or right to get the split where you need it to be. This is the primary use and reason I have the system. For most other types of filters there is no real advantage over traditional screw on filters, IMHO.

For the cons: the system can be awkward to use at times. Because the filter holder slides onto a ring that screws it the threads on the front of your lens, putting the system on and off the camera can be tedious. This becomes especially bothersome when i decide i want to switch lens. With the ring on, you can't attach your normal lens cap. Cokin does make a lens cover that will slip onto the holder ring, so you can just mount a ring on each of your lens, but since you mention that you have an 82mm lens, you will be using Cokins Pro size filter and holder, so the rings you mount will be plenty wide. I find that that is an annoyance for lens storage in my bag.

Additional con: the system increases the chances of vinyetting on very wide angle lens.

Despite the cons, if you use ND filters a lot, it makes having the Cokin filter system worth having.

As for a polarizer. I prefer a screw on. You can use step up rings to make one good quality polarizer work with all of your lens at a very reasonable price, and certainly for less than the cost of the Cokin system. Just buy one that fits your largest lens (82mm) and get the step ups for your others.

Yes, lower resolution will effect images quality, but as has been pointed out, this is really only a problem depending on the final presentation of the images. No problems for small prints, or images that will be posted to the Internet at 72 dpi. The problem will rear its head when you make that "perfect capture" and want to blow it up and print at a very large size, and you find yourself wishing you had shot the image in the highest quality resolution your camera would allow.

Memory for image capture and storage has become so reasonablly priced that shooting at lower resolutions to save disk space is no longer the concern that it was back in the early days of digital capture. Heck, I saw a good brand name 3Tb external drive on sale this past weekend for $159! And as was mentioned previously, you NEED to be backing up your images externally anyway, so no reason to not have ample storage to allow you to shoot maximum resolution files. Don't let storage be the limitation that prevents you from producing the "perfect" 30x40 print that is the crown jewel of your photographic endevers.

I print using gloss, matte (a rag art paper), luster (semi-gloss), and for some images a pearl (sort of a pearlescent sheen, somewhat metallic). It all depends on the image. I have a series of macro shots of blown glass that I always print on gloss, for example, while most of my rustic still-life images are on the matte art paper (Entrada Rag). The semi-gloss "luster" finish is probably my favorite for most things. It is less reflective than gloss, but has a nicer color saturation and "glow" than a matte finish. Recently I have enjoyed printing a number of my images on a "pearl" paper, especially landscapes! It is wonderful for landscape images that feature sky and water. It makes dark blues, orange, pinks, and purples glow.

My lab, which I use for prints over 13x19 offers all of these four surface options, so I can pretty much match up my large and smaller prints.

Mount Rushmore is a national monument in the Dakotas, and is a mountain carved into a sculpture depicting four important US Presidents. Monument Valley is an incredible scenic location in Arizona dominated by "monumental" mesas and towering rock formations. If you are a fan of classic American western movies, you have probably seen Monument Valley.

As for a polarizing filter, it is, IMHO, one of the must have pieces of equipment that any photographer who shoots outdoors needs to have in his or her camera bag. They are extremely useful, and in some conditions positively essential. They help cut glare and reflections (especially on water), help cut through haze, can improve overall contrast, and can help enhance colors (blue skies are bluer, clouds "pop"). There are some things to learn about using them (they can cause a vinyette on wide angle lens, they are not very useful on overcast days, their effect depends on the angle of the sun relative to you shooting direction) but the learning curve is not very steep. All in all, a polarizing filter is a good investment, especially for shooting in the sunny Southwest.

I've used Redimat.com for quite a while now for my fine art photography business. Their prices are good, and you can buy either pre-cut mats or blanks, depending on your needs. They offer a good variety of both mats and backing boards. There are also price breaks for buying larger quantities.

I buy some pre-cut mats from them, but more often buy blanks and cut the windows myself, as it cuts my production costs down substantially. I have been using the Logan Simplex 750 mat cutter, which is a good model for those cutting mats frequently. You can generally find good deals for new ones on eBay at very reasonable prices.

If you are going to be cutting a lot of mats for sale, it might be worth looking into Logan's more expensive cutters (Framer's Edge or Platinum). I am planning to move up to one of those models soon.

As for plastic sleeves, Clearbags.com is definitely the best source IMO.