The alrger the footprint of the tank, the better. It provides larger surface, important for the exchage of gases and larger swimming place. I would go for the largest footprint possible. Eheims are reliable workhorses and pro3 are real monsters. You could get that beast instead of your 2028. or you couple two same filter types. Normally all ro are good enough, from no name to rowa or such. I think that in thread about other water conditioners tahn prime it is alink to the article which staes that activated carbon helps to catalyse chloramines and chlorine binds to it.