I use the IntelliChlor. I got the IC40 with power pack for $775. I just looked on e-bay. There is a new IC40 with power for $499 (the average seems to be around $700). I don't know what the other brands are selling for.
Whatever you go with, get the largest size cell. That way you can run the cell at a lower output and it will last longer.
Good Luck