jtag,
Do you own an IC40 now??
I am a highly biased Pentair kind of guy, but unless you have Pentair automation, even I would not recommend a standalone IC40..
If you do not have a SWCG now, I would go with a CircuPool unit, or a Hayward T-15 style system. You get much more operational feedback from those systems compared to an IC40..
If you just want an IC40, I would look at this link..
Pentair IntelliChlor IC40 Complete Salt Chlorinator System
Makes sure any cell you buy is rated for at least 2 x the volume of your pool.. A 20K pool needs a 40K cell.
Thanks,
Jim R.