since you are saying you are going with, i am assuming that you do not yet have th tank, if this is so, i agree, don't bother with a hang on, get a sump and if you don't yet ahve the tank, check ou t built in overflows, they are more reliable and for us to get a built in over flow, was only like 50$ extra, you'd be much better off
scott i like the bak pak, but a 75 is kinda pushing it for them, to answer your Q, if budget was not a prob, i like the berlins, 2d and the ramora's by aqua c they are a bit more than the cpr bakpaks but are much better off, and if i were to look at a 55 i would probably go with a bakpak(but not a 75)
anyhow, back to the original Q, get the built in overflow,a nd construct your own sump, for little or no money, add a pump(and this would be the majority of the cost), gives you more stability for your tank, and a place to hide your pumps and heaters adn such, beyond that, i would have lr and a dsb, and an in sump skimmer(so it is not visible, ou could also add some lr and sand to your sump to make it even more of a benefit, through biological filtration
and forget the hang on filters, they will later become a problem for nitrates(emporers and magnums included), and yes i have them myself, so i am not stating based on wht i read, but what i have learned and used
HTH
