Another factor which has not been mentioned yet is the physical layout of the room(s). Is it square or an almost square rectangle? Is it a long narrow rectangle? Is it L-shaped? Any side rooms or spaces that are set off from the main area? How high is the ceiling and what material is it made of, acoustical tiles?
Orientation of listeners in relation to the DJ is important. If people will be close to the DJ, and there are also people a significant distance further away which would require blasting the main speakers, then it would be too much for anyone up close. In that case, perhaps multiple speaker pairs would be a better option.
I used to frequent a bar that had one large room that was maybe around 2500 sq ft, and a rectangle of approximately 3:2 proportionately. One end of that room had pool tables, the other end had a small bar and several dart boards.
The pool table end was served by a pair of Yamaha 15"-and-a-horn pro speakers. The dart board end of the room was served by a tiny pair of Bose satellites and a matching sub. I believe this may have been an Acoustimass (sp?) system. I am not a fan of Bose but not a hater either. Likewise, I am not a Yamaha hater. Indeed, I think that company does a lot right and I have a pretty high opinion.
In the end of that room being served by those two little Bose speakers and matching sub, music sounded sweet. The other end, music sounded like crap.
Pro speakers are designed with a priority of high efficiency, which means that frequency response can have peaks and dips that would not be typical of decent home audio speakers. It is assumed (an unwritten "rule") that pro speakers need competent EQ'ing to sound good. Competent EQ'ing is easier said than done, i.e. most who think they can do it, can not. Without that competent EQ'ing, pro speakers, especially mid-to-lower grades of them, will not sound as good as decent home audio speakers, and some of them can sound downright awful. So IMO it would not be a good idea to simply hang up a couple of pro speakers fed by a powerful amp, because of sound quality and also because of (possible) close proximity to your patrons' ears.
IF there is some space (like a dance floor) between the DJ and the area where your patrons will be seated, then the pro speakers fed by a (relatively) powerful amp may make more sense. But if you do this, invest in an equalizer and get someone with pro experience and a good ear to set-up the system.
my .02¢