I'm a little late to the party, but there is a big difference between a "filter" and a "purifier."
Although most folks say you don't need a true purifier, I take no chances with the crypto.
We use a First Need purifier - it's around $100 and is a true purifier. No mud, no sand, no giardia, no crypto. Just FYI - again, most folks say you don't really need anything more than a filter in the Blue Ridge - but hey, if the world falls apart, I can filter water out of the Hooch below Atlanta, too! LOL