I have a set of SM-115's, they aren't junk but could be better. I did add 4 braces each from the baffles just behind the woofers screw mount to the back of the cabinets. There are gussets from the backs to the sides from the factory but more bracing wouldn't hurt any.
Just out of curiosity, what crossover rebuild would be required, do you have specs? Who knows, maybe some day...