willie: hey, just wanted to throw one more option out there, since I recently was debating on getting a carx, but for at least right now I have decided not to. Instead, I plan on using Randy's DIY 2 part Ca and Alk recipes and a litermeter 3 to dose those. And to use kalk for the remaining daily topoff. I've already started doing this, except all manually as I haven't purchased the litermeter yet. Logging my test results and what I've been dosing over the last couple of weeks and I'm definitely seeing my average daily consumption. Going to continue doing this manually for a bit longer, then get the dosing pump. Hopefully I'll be able to 'dial in' the Ca and Alk rates & it will hold steady....
Cost-wise, not sure there's really a savings going this route (at least with the litermeter). But I think this is a viable alternative, so I wanted to mention it to you since you're currently at the same decision point I was recently.
hth,
rob