Aquasafe Replacement Filters

[Jaws]

I think I'm way past due for replacing my filters on my Aquasafe 5 stage 100GPD unit but I'm not sure what I need exactly to do so. I don't use the DI cartridge so from what I can see I need replacement filters for the three large vertical chambers, the horizontal chamber above and then there's the top horizontal chamber that is see through and contains a sponge filter of some kind. The sponge has almost disintegrated and the water is pretty merky. Am I best to just buy a box of replacement filters eventhough they come with the DI filters too or is there a better way? Thanks.