Deltec Twin Tech, it’s expensive but fully automated and very simple to use. I have the 1500 version and it’s a work of art. It looks complicated but it’s not really.
I have tried a few different reactors in the last couple years, most recently.. GEO, Dastaco and Deltec. They will all do their job, it'll just depend on your budget. GEO are prob the cheapest route but if you set it up correctly with the right gear; it'll cost you prob right around $1000-$1200. A good dual stage regulator with a good solenoid and needle valve is most important.. and a good peristaltic pump. The automated calc reactor like the Dastaco and Deltec twintech will come with almost everything you need. Deltec does not come with a regulator. Both of those units will run you around $2000. If you are lucky you might find a use one go up on the market place but rare....
I've been using my LifeReef reactor for 7 years without fail. Super simple with very few parts. When my demand went up adding an extension was also incredibly easy.
aqua excel offer great calcium reactor for the money. Got all set for under 1000$cad (including regulator, co2 tank, ph controller, etc) and its running great since I got the CR60 2 month ago.
What size of tank are you running.
I run a Tuze 3171 with Tunze manmade media on my 120.
Requires no feed pump and is priced well. Small footprint as well. The 3172 is good for larger tanks.
The real issue is a good carx system is still going to be $1000ish.
Get a good 2 stage regulator and your set.