By themselves, I would say they might struggle in such a big room. But if you're willing to add a sub or two, they might work. How high is the ceiling?
If you can afford it, I think M40.x will be a better fit for your room. But SHL5+ should work with a couple of subs.
P.S. I have owned SHL5+ for a few years now. They used to be in my main system (room: 20x15; 12 ft ceilings) and now in a much smaller home office (12x13 but 20 foot ceilings). They excelled in both rooms. Easily amongst the top 5 speakers I've owned thus far. Many speakers have come and gone but I could never bring myself to part with the SHL5+.