great forum guys, its my first post so go easy on me

im looking at which van system to get, im just startin out (domestic work) and the budget is tight so i was looking at the diy setup from purefreedom for £739,but will probally go for the 400ltr tank, my question for ye experienced users is, if i was willing to spend a few more quid what should i change about this package? should i get a larger Deionisation Filter? different pole? or anything else? i would be greatful for yer thoughts, thanks
heres the link
http://www.purefreedom.co.uk/self_fit.html