If your water is that bad; Joe, you would be much better off with a softener, iron filter or just a sand filter ( a softener tank with just sand in it) with an automatic backwash head. That way you buy it once, let it clean itself and you won't have to worry about it anymore. And no more cartridges to buy.
When cartridges plug up, the water flow is cut down. When you restrict flow, low pressure ls the symptom. The guy that coined those things as "Whole House Filters" should be taken out back and shot. The only way a filter that size can filter out anything that would be harmful, would practically take your flow down to nothing. Take Reverse Osmosis systems. The pre and post filters are simply whole house filters, then the membrane has layers that squeeze practically everything but water to drain. And they are used for one faucet which is augmented with a storage tank. Try running your whole house off one of those.
The lakos seperator that Redwood mentioned is a great little unit. It doesn't filter anything, it simply spins the sand to the bottom of the unit for dumping later; and lets the water pass without the sand. No moving parts but the water itself.