if you buy the 2080 their is a media kit that is much cheaper than buying it seperate
i have no idear why the 2078 has a faster flow rate than the 2080
i think its all down to space the 2080 is a massive filter were you can fit the 2078 in a smaller space
if you were to buy 5 x 2080s that would mean you will have 10 x intake pipes in your tank
thats alot of pipes
but with the 2078 you will only have 5 x intake pipes
the good thing with the 2080 and the 2 intake pipes is you can do what i done take 1 intake pipe direct to the 2080 then the 2nd pipe you can take it to a big pond bucket 1st then out of the pond bucket to the 2080
this gives you a massive pre filter and much more sponges than a FX5