I would just go for the FRVs from Firepower. The Adia system (while very clever), is just a way for installers to avoid doing calculations and reduce call backs. For any enthusiastic homeowner, the FRVs accomplish pretty much the same thing.
I installed them last year and have been extremely happy with them. The distribution of heat around the house is now perfect, and balancing the system now takes 5-10 minutes, and not hours/days like with traditional balancing.
I designed a calculator which helps you calculate the ideal flow rate for each radiator based on the rooms heat loss & radiator spec. The good thing is that it accounts for mismatched radiator sizing.
You can buy them from the openenergymonitor store:
And Glynn did a video about them which is on the tube: