The prices from GHL to us are comparitive, of course the pump and motors are sold to us more expensive so they are priced accordingly.
I can assure you upgrading or downgrading comes with strict regulation and monitored by us. Fair play is imperative to how we run our business model. An upgrade or downgrade is usually only allowed if we do not have stock to cover the dealers requirements as in at the time Reef Shoppes case.
One day I will stop being so open
In regards to SA3 vs SA2 - most go for the SA3 as they do like to balance the system properly, even if you are dosing only 1ml a day, its still 1ml every day. On the other note they may wish to have a pump on hand for dosing something else. And when dealing with the slave unit there are multiple options for the 3rd pump.
Edit - looking at stats for October - the SA4 is outselling the SA3 and has done for the past 7 weeks!