I have been using a MRC CR-2 on my tank for the past 6 monts with no complaints. The only thing I would suggest that you make sure you have in whatever unit you choose is the following: A spraybar attachment that will disperse the C02 throughout the entire media thus lowering C02 consumption. I would alsso recommend that there be a probe opening in the reactor so that you can monitor and attach a controller the effluent PH from inside the reactor.
Here is a link to MRC as it was not on your list.
www.myreefcreations.com