The radio is the same, won't matter which receiver you use if you're wanting to stick w/ base and radio. Upgrading receiver won't change this. 


You can turn off RTK and run SF1 by going to the tower icon on the right side of the receiver pages and then where it says mode - vehicle turn that to OFF. If you don't need RTK I'd just do this and you don't spend anything. 


If you have other RTK receivers laying around, you can setup your own base with just a base station harness and a power source like a 12v car battery and tripod or post to attach it to. You will need one of your displays hooked to that harness the first time to setup that receiver as a base and choose survey etc.