i go sa lower rated speaker powered with a amp rated 1.5 to 2 times the speaker's rating.
if for example the 500 W speaker is @ 115 dB SPL at its rated power, the 1000 W speaker @ 115 dBSPL at its rated power, the 1000W speaker needs 3dB or twice more power for the same SPL .same loudness pero mas power hungry yung 1000W, mas mahal pa yung bigger amp.
also go for more sensitive speakers.
and speaker's are not incandescent lamps, higher power lamps outputs brighter lights, higher power speakers doesn't mean louder sound...