will this system replace my phosphate filter

In a way. Phosphate filters release phosphates into the water which attach themselves to minerals. This prevents the minerals from doing much damage. The KR units actually remove the minerals from the water to prevent damage. Another difference is that Phosphate filters require no holding tank and can pretty much run continuously until exhausted; where the KR units produce 24 to 30 gallons of very high quality water per day with a 2.8-gallon storage tank limiting how much water can be used at one time.