Dave what do you anticipate as your daily water requirements now? and in say 1 year from now?, what is your TDS (Total Dissolved Solids) from the tap and do you know what your normal water pressure is?, what do you currently use as a work vech and are you thinking of changing it to something else? the answer to these questions will really put you in a better position to see what equipment you may need both now and in a year from now.
As with all things ...you could walk into a shop tommorow and be sold an all bells and whistle system which could be overkill for you and in the same sense you could be sold something that nowhere fits your situation...so having some idea of your possible usage will really enable to you save your pennies...
Just a few tips...000tds water is 000tds water but poles & brushes are not all equal....Scrub, scrub...rinse, rinse and then rinse some more

Cheers
Dave.
p.s The whole water purification thing is much hyped but suffice to say the working of it for 'us' day to day is very simple indeed that even I can understand it.