I went with the filter/softener system from Clive Coffee
You may not require a softener. You should determine the ppm with the included water hardness test strips included with the unit. You can also buy them here: http://www.amazon.com/gp/product/B00EA9 ... detailpage which have the appropriate ppm range.
Note that the owners manual does not discuss the recommended in-line water pressure anywhere. You must go to "For tips on plumbing in espresso machines: click here" at the middle of the Lucca M58 product screen which takes you to this PDF http://www.clivecoffee.com/assets/plumb ... achine.pdf. Here I learned that the recommended water pressure to the machine should be 25 psi or potentially void the warranty. I found out from my plumber that our incoming municipal water pressure is 60-65 psi. Hence I installed a pressure regulator which is set at 25 psi.
Source : http://www.home-barista.com/espresso-machines/lucca-m58-by-quick-mill-reviews-and-owners-thread-t34687-160.html