I installed an Aqua-Pure by Cuno softener a year ago. http://www.aquapure.com/sysproducts/cws.html
I had my plumber pick it up through his local distributor. With tax, it was around 800.00. The unit will soften using either sodium pellets or potassium. It was simple to hook up and I'm very pleased with it's performance. Our water 10 grains hard and was clogging up my on-demand water heater, shower heads and aerator. Before I installed the unit I was cleaning these out every 2 weeks, now I don't have to touch them. I would highly recommend one of these if you can find a plumbing professional to help you get your hands on one. I had quotes from all the TV advertised companies - they want around 5K for their systems. Their hardware doesn't cost this much - they make their money on the service contracts that sell with the units. If you get one of these sales reps in your door, good luck getting them out of your house without a signed contract. They almost had me and my wife sold after they did an in-house demo. I had to kick 2x sales reps out of my house - both with a major attitude after I politely declined their contract because I told them I wanted to shop around.