John,
I only have first hand experience with the DSR112 and DSR115 (I assume you are looking at 15" speakers for a club install?). I have heard the NX750p, but it has been a few years.
The DSR115's get silly loud. They are a little bit much up top and generally need a little HF cut. They aren't kidding about the 136db output. These are the punchiest of the powered 15" I have heard.
The NX used to get more love back around 2008 time frame IIRC, but I don't hear much about people getting them these days.
What kind of music will the club be playing? Are they planning to have a sub?