Water filtration is a can of worms* ;)
What is the correct water filtration depends heavily on what water you have to start with. anything from a brita Jug up to R/O is the right answer.
The water filtration primer here is a good place to start http://coffeesnobs.com.au/YaBB.pl?num=1300415170
I have just recently moved house and the new place has a water tank while the town is on artesian bore 800mg/l water :P Due to the proximity to the coast the tank supply is heavily tainted by salt and personally undrinkable in coffee. Currently using R/O water :-)
So more info needed and welcome to the lever gang too 8-)