Types of speakers to create nightclub style sound?

As an option to Funktion One, you may look for a used VOID system. Overall, expensive but good sounding when set up properly. Do not forget, Visual Appeal is also nice for a party. It makes people pay attention to the sound system and draws them into "sound quality" topics and conversations. In this regard F1 and VOID are way above the other modern black boxes.

I can answer the question because I have this type of a listening space/venue with very similar needs. My space is 550sq ft, and at times I have 20-30 people listening at party levels. Other times, quiet listening.

From other posts -- KEF, Goldenear, Cerwin Vega, QSC, Mackie, JBL are:
1. either not capable of high output with low distortion
2. Are just not high fidelity PA speakers. Like QSC. Yeah, they're PA speakers.
3. Too colored sounding -- like Altec VOTTs or many other vintage designs. A "decent" option out of all those would be the Klipsch LaScalas.
Altec 604 are not bad but start to fall apart at high levels, so not suitable for the OP requirements.

You're not a PA rental company and you do not need to select based on the motto "work horses of the industry". Keep in mind, this is what QSC, JBL, EV and most others design for. On the plus side they're consistent -- like McDonalds.

IMPORTANT:
In my view the key to "listenability" at high output levels is lots of headroom. You need PA that's designed and built to the Standard of Highest Fidelity and Listenability. By listenability I mean being able to listen at higher than usual levels for extented listening sessions -- over 6 hours without fatigue. Another important point to consider is how much more output capabilities are required when there are 15 or more people in the room.  Going to someone's place and listening to a system will not be a good indicator of how much output you may actually need, when there's a party goin'! 

THREE systems come to mind:
1. Funktion One
2. Meyer Sound
3. Tannoys

I have all three. Each one has it's advantages and disadvantages:
If your space is OVER 600 sq.ft. I would recommend F1. Go with Res2 (or AX88+F115 for higher output) + a sub or two.
If your Space is UNDER 600 sq. ft, go with USED Meyer UPA-1p + USW-1P subs. They are powered so you do not need amps. Compared to most speakers listed in this thread, the Meyers are in a different league. They sound very good. 

If you're on a tight budget get Tannoys CPA15 or V12 or i12 and add a sub or two. The mentioned models are highly musical PA speakers -- much better than most.

ANY OF THE ABOVE CAN and SHOULD BE PURCHASED USED! This is the only way to get good quality PA gear and not pay over $10k

P.S. no experience with BagEnd or Bose so my comments do not apply to those.

I am familiar with QSC CP8. I would rate the Tannoy V8 over the QSC's in terms of sound quality. Also the V8 can be purchased for around $350 used, for the pair. 

All that being said, the Tannoy V12 would outperform both of the above, no contest. Hence my original recommendation.

Who cares about the op? Aren't we just venting out in response to the usual audiophile equipment non-sense talk? 
Oh wait, no. OP had a good question so we all trying to help him. Yep, that's it!

"Night club systems are PA systems, not audiophile systems"

Yes. But I find that good PA systems sound closer to live sound than almost any Audiophfile systems.  One exception that comes to mind would be Avangarde trio -- that one was good. 

OP wanted to have music parties. This is PA sound territory -- one needs to move some air!

For any kind of electronic music party you cannot count on dual 10" woofers for bass. Real bass with impact and low distortion needs to be produced by a sub or a pair of subs. Pair of 15" should do. But also you need midbass with impact == big horns like Funktion one or high efficeincy PA cabinets like Martin Audio or Tannoy. Big horns wont fit your room size so go with good PA direct radiators like  Martin Audio or Tannoys. Lastly, an expensive but awesome option is Meyer Sound System. All powered so nothing to mess with. UPA1p or Upj1P + matching subs.

That would be a kick butt system to throw parties. A bit overkill in a 28m2 room. So... if you need to save money or need to make it work on a smaller budget, get a pair of Tannoy V12  ($600)
+ Lab Gruppen E amp
+ pair of powered subs
+ an analogue active crossover.
You would spend half as much and get very good sound. I have Funktion One and Tannoy speakers so I've listed to both extensively. In a room around 28m2 you will be best off with a pair of Tannoys. V12 or V8 or  CPA15, those three models sound very nice. All need a subwoofer.

No QSC. Used and heard on a few occasions. They sound like crap. Jesus, who in their right mind and not deaf would recommend QCS? 

 Then the solution is obvious.  Martin audio which you have already found or if you need to be on a smaller budget, used Tannoys.