PA System Stereo or Mono

Hi all, I am putting together a PA system for use at parties and weddings etc. I have a pair of Yorkville pulse speakers (15" woofer and
compression driver) and a pair of custom built scoop bass bins each with a 15" Max Professional (Canadian brand). The amp is a Yorkville AP4040 and can deliver 1200watts per channel into 4 ohms. Should I run the highs of one channel and the subs on the other. Or should I run it stereo and buy a passive crossover. Or should I get two more channels of amplification? Maby even get rid of the scoops and get a single active subwoofer. Any suggestions?
For parties stereo isn't really required, I would suggest running it in mono for now, using an active crossover - then when you can afford it, get an extra amp and run it in stereo using the same active crossover.

Big advantage of this is that you have some redundancy for when something dies, by a quick rewire you can keep the music playing, and still of decent quality.
AFAIK, most big club systems, using multiple loudspeakers to cover all dancefloors, chillout areas etc, are mono. All rock concerts are in mono, only some reverbs and other effects are stereo. There are exceptions - some electronic music artists perform live in stereo, unplugged concerts are "stereo" so to speak.

But yeah, 99% of the punters will not notice stereo if it bites them in the a** - alcohol+girls=f*** the sound quality, even for me;)

Maybe if you placed speakers in the opposite corners of the room, then someone will notice that some instruments are playing in one corner and some in other. Actually, that was a practice I used when DJ-ing at one party - I had no monitor speakers and I wanted to hear the mix, in stereo and did not want that nasty HF horn right next to my ear. So speakers in opposite corners and I in the third corner. Worked very well and will be my preferred tactics for smaller parties in the future.

For the OP's system - by all means, run it in mono for right now. But I'd suggest you to get another amp in the future - redundancy and added headroom are worth it. And stereo:D As for crossover, I'd suggest you to get some cheap Behringer, but if you want to get something more advanced, Samson S3 looks good - 3- or 2-way stereo, 4-way mono, has limiters and delays. And is cheap - 159€ (~250 USD) here in Europe.