look at it like this...people here in usa, in podunk towns, buy more berlin skimmers than anything else...does that make them good?? ...no
the six foot aquamedic skimmers with dual ocean runner 3500's are weak and sluggish, for the money they cost they are a complete waste.
i say this because your money would take you so much farther if you invested it in another skimmer.
by what standard am i judging these skimmers??
well, as a general rule of thumb, i like to have a skimmer that for sps tanks injects 500 lph of air for every 100g of display tank, for mixed tanks i'd say at least 300lph for every 100g. i also look at power consumption, design, build quality. it's not that the aqua medic is SO horrible, it's just that for the same money, you could probably get a skimmer that has twice the power and a better, more efficient design. also, the other thing i hate, if you plan on using the multi, is looking at that big nasty pump hanging in the tank, if it's in the sump, then it's not so bad.
and like like said, if you have a 55g, then it might be o.k. but again, if your buying it new, then there are too many other skimmers that are better for the same money.
take this skimmer for instance, 1200 lph air injection, @23 watts, $295
http://www.aquacave.com/octopus-extreme-160-br-protein-skimmer-br-by-coralvue-2199.html
and as far as alf nilsen warning about overskimming...
ring...ring...
the 90's called,
they want their methodology back.