What stands do you have? do you know the weight rating for them? Some don't hold much! Compare that to your speakers... if its close maybe not a big deal. but a little bump could send those new speakers tumbling if too heavy.
I bought VTI stands for my 34# BMRs... supposed to hold up to 100#. I don't believe it, but I will say they are almost the same weight as my speakers, especially filled with sand!
And if you can fill yours with sand, do it. A 50#bag of
kiln dried sand is $4-5, or Clay Kitty Litter. Just wear a dust mask when filling them, and they should be a bit more sturdy. Floor spikes may help too (can't tell if yours has them).
But more importantly: How do your new boxes sound?