As an alternate to using the Driverack, you could consider the inexpensive DBX 266XS for the sub only. It has a peak stop limiter, as well as compression. Since your Mackies already have speaker protection, you don't really need a peak stop limiter for those. But you could use one side of the two channels of the 266XS for the Mackies if you ran them in mono. There's also the Behringer CX3400 crossover that has limiting. The downside is, it's Behringer and the low cut is set to 25 Hz. IDK what you're using for a crossover for your sub. Many are two channels stereo and three channels mono. And most have adjustable freqs ranges + a low cut. The DBX units use a 40 Hz low cut, while some others use 25 Hz.