How many water filter systems do you need?!

I know water quality isn't the best that we have here, and so a lot of homes install their own water filters. We've used a few different brands and types but still I find the water not really that clean. What about you?

That leads me to wonder if we actually should install more filters at different points leading up to the kitchen where we need clean water for consumption. Don't know which is the truly recommended brand to use either as everyone claims theirs is the best around.

Any tips, anyone?