If you're going to stick with that one meter (or meters that HCFR supports), and don't need workflows and reports and are content with what you're getting from HCFR, than you don't really "need" the paid calibration software. There are other benefits, of course, such as access to their support network (as opposed to waiting for an answer on a forum), support for more meters and/or as they become available, auto-calibration, and profiled meters among other things (though the latter not needed in your case).
I think you'll find many of the users of the paid calibration software started with HCFR before moving on; in my case, I made the switch to Chromapure when the HCFR devs went on a long hiatus. I like my software to just get out of the way, and Chromapure is like that for me with its ease of use. Anyway, you won't go wrong with Chromapure/Calman if you decide to go that route.