I am new here and I am preparing to buy my first arranger (right now I'm playing at home with a cheap Yamaha PSR-83 plugged into a Roland XV5050 sound module) so I am not qualified to address how a speaker sounds for an arranger in a club. However, I have done DJ and karaoke shows full time for 10 years so I can tell you about my speaker experience.

I started with 2 200W 15" non-powered EV speakers on stands powered by a Peavey XRD 680+ mixer amp with build in effects. Good sounding system for small gigs where you don't need a long throw. The Peavey had to be serviced once but the speakers still sound like when they were new--10 years later. Great sound for the money. 300W total.

My second system is 4 350W powered 12" EV speakers and 2 400W EV single 18" subs powered by a Crest CA 9. I got a Mackie 14 channel mixing board and a Rane crossover. This system gives me a lot more power. However, I had to have all the 12" speakers serviced because there was a design flaw where the heavy amp would fall out of place. They paid to fix it, though and the problem hasn't recurred. This system gives good clear sound, but I have occasional problems with humming. I would probably not buy another powered speaker for a mobile application. Total 2,200 Watts.

My third system is all big JBL SR II stuff. 2 JBL 1200W double 18" subs each powered by a Crest CA12, 2 1200W double 12" speakers with 2" horns powered by Crest CA9s, and a 600W floor wedge powered by a Yamaha 5000.
I mix with a Mackie Onyx and control with a dbx Driverack PA. Reverb and delay are with a Lexicon PCM 80 and PCM 90. This system is the best and clearest by far. 10,000W at full blast.

Here are some lessons I've learned.

Powered speakers are problematic at times and heavy.
Rack EVERYTHING!! or you'll be sorry.
Don't UNDERpower your speakers. In general you should have at least the number of watts going into your speaker that is in between the continuous rating and the peak. For example, my JBLs are 1200W continuous and 2400W peak. You should send them between 1800W and 2400W each. I send them about 2400W at peak. This prevents my amps from overworking. Underpowering will blow speakers quickly. I found this out the hard way. Check with your speaker manufacturer for specific recommendations.
NEVER clip anywhere. NO red lights on anything from the gain light on the mixer to the LED on your amps.
Don't buy cheap mics. You can't go wrong with a Shure SM58. You can pound a nail with one and it sounds like new 10 years later. I have one from the mid 80s that looks like a joke, it's so bent up. But it sounds great!
Better to have too much PA and run at 50% volume than too little and overmodulate. The latter will grate people nerves and ring in their ears and they'll leave your show early. Quality and clarity are what's important. The person who complains that a show (at 60 db) is too loud and loves an Aerosmith concert (98 db) is really noticing the difference in quality and clarity, rather than volume.
Don't skimp on subs or people won't dance. Try cutting your bass one night and watch people walk off the dance floor. Again, quality and clarity in your bass punch are important. Don't overmodulate.
Understand that at my shows I go from singing Elton John or Merle Haggard to playing 50 Cent and the Black Eyed Peas and with the hip hop stuff and dancers you need a lot more volume than one would need in a Piano bar, especially playing at dinner time.
My goal is to get a Ketron SD1 Plus, Tyros, or Pa1XPro and merge it into my shows. I play 6 nights a week and as I learn songs I'll just play them and sing them instead of singing a karaoke song. Hopefully, with a lot of hard but enjoyable work I'll be able to do a show of just me singing and playing.
I am lucky in that I DJ all the time so I have an instant outlet for playing in public even when I learn my first song or two. I can't wait. And this forum has been so helpful and informative for me as I make my decision. I can't be helpful on arrangers yet, but I'll chime in on ancillary issues where I can be helpful until I know enough about arrangers to speak from experience.