You can add a X3-S to a collective with an X4 to get you a salinity port. It also has 2 sense ports and the sense ports seem to get used quickly. Hydros did not have a salinity port option when the X4, X2 and original X3 were introduced. The first controller to have one was the X10 then came the Launch and after that the X3-S. The X3-S is basically an X3 without a pH port but with the salinity port added instead. The Launch has 4 drive ports instead of the 2 on the X4 and they can deliver more current than the ones on an X4.
I have looked at this option. actually looking at them all.
For my display tank I actually think a Launch,x3, SOL, 2x wifi strip or xp8 and Ivy will do everything I need for now on my DT and will ad a blenny when the Maven is released and vetted by others.
For my mixing station I think a single Launch will work.
then ad a bunch of 4x float switches,6x optical sensors, 2x salinity probes, dual tds sensor,4x 12v NC solenoids, c02 solenoid, push button box and an auto feeder.
I think that is my wish list. I am sure I am missing things and there will be more that I want to ad.
I am hoarding pennies.
Just priced everything out thru Top shelf aquatics, have never used them but had an easy site to navigate.
i am around $3k for everything i want minus bus cables to connect everything. in reality it don't think that is to bad, just a hard pill to swallow.