A simple graphic EQ (or parametric) is all you need for your basic MI grade powered cabinets.
Especially for work on the bar/club level.
You will never dial in better limiters then are already provided by the manufacturer in there product, which besides adding a delay for a satellite speaker, is the only feature a entry level driverack device would provide you.
There are a lot of products on the market that do very little...if anything to improve performance.
The Driverack PX is one of them, the other is a BBE Sonic Maximizer.
Yet, people still buy them and think they make there gear sound better.
What ever works for you I guess.