My two cents, step up to the 26-99 and keep your 15-58 in case of a emergency, the slight step up in watts used shouldn’t break the bank.
Another good option, and I wish Grundfos would offer it, put replace the 15-58 with a Taco Delta T pump then no matter how many zones are calling for heat, you can always keep your Delta T where you want it. I’m running one for my house at the moment, heat load can very wildly, any combination of DHW, heat, snow melt, or all three at the same times can drastically vary how much flow is actually required, so far the Taco Delta T has worked neater than a skeeters peter.