If that idea is attractive then I would suggest you buy the higher power amp:
https://www.bhphotovideo.com/c/product/1322845-REG/jbl_vma1240_vma_1240_5_input.html
And you could stick with something similar to the Rockville speakers in that eBay combo:
https://www.rockvilleaudio.com/wet-5b/
Add ala carte the number you need, and set the tap on the back of each speaker so the TOTAL wattage is about 80% of the 240 watt amplifier. If you buy 10 speakers at $58 and set the tap to 20W each and the amp for $450 you're near your budget not including wiring. You could even add a 1-gang wall volume knob/input selector that you could switch between an announcement mic and music:
https://www.bhphotovideo.com/c/product/881073-REG/jbl_csr_3sv_wht_csr_3sv_wall_mounted_remote_contro l.html
It's ABSOLUTELY not "dance" or "band" loud. Not even close. It'll probably hit 85 though.