Use Reach M+ as Base for Reach RX

I have a REACH RS+ and thinking to buy a new Reach RX. I know that the multiband REACH RS2+ is the best option for maximum accuracy. But, is possible to use the REACH RS+, monoband, as a base, until I update all my stuff?..thank you for your assistance.

No, you will need a dual band base. A 2-series can be a base for a M+/RS+ but not the other way around.