Katadyn (for water filters), not Katahdin (the mountain).

You can rig up a gravity system using almost any kind of filter. I've done it with a Katadyn Hiker Pro replacement filter and with a Sawyer, using existing water bladders and tubing from US Plastic. The info I used can be found here, in the posts by "obxhiker."

I gave up pumps long ago--they take a long time and I always put my back out bending over the water source.

Like ETSU, I've had serious problems with the Sawyer filter clogging. Check it the night before you leave for a trip and backflush if it isn't working. Backflush and then use a bleach solution after every trip, as in their directions for storage.

For a group, I'd suggest a gravity system. For solo trips, the Sawyer Squeeze or Mini. Take some Katadyn or Aqua Mira tablets (chlorine dioxide) for backup, no matter what system you use.

I would never consider Cabela's a source for lightweight backpacking gear. Well, maybe fishing tackle, but it is a hunter/fisherman store, not a backpacking store. Just because one person has done a long distance trail doesn't make him/her an expert. Here are a few more informative sources about the kinds of systems available, although do note that they are trying to sell you the stuff:

Outdoorgearlab.com

REI

Finally, the most authoritative sources are standard medical resources such as The Centers for Disease Control and the Mayo Clinic.