hey i had one of this on my tank and it will do a better job at turning over the water in your tank than what you have now .
http://www.aquacave.com/detail.aspx?ID=79
take a look at this one that is if you did'nt already get one......
http://www.marinedepot.com/ps_ViewItem.aspx?idproduct=UJ3311&idCartRow=25085198&isKit=0
it's the most silent skimmer that i've ever owned
i have to clean my collection cup every three days and it's not because it's ready to overflow but because of the smell of the s*@# that's coming out of it..............
If you say the overflow box is 600 gph you might want to buy a bigger pump because eventually your going to add stuff to the tank ( phosban reactor,uv sterilizer) you know stuff that will need a supply so maybe a 900 gph as for brand i've never used any of the ones you mentioned but i have used...
i'd call them while the rock is in transit once your sure of the weight that way there wont be too long a wait for the rest of rocks and whatever you can squeeze out them for the mistake they made to arrive..........