Four speakers are always better than two! You are going to get more watts out of your amplifier!

Ignore Ohm's Law - because there are lots of other considerations rather than just impedance!

If an amplifier is rated at 450 watts per channel at 4 ohms, connecting two 8 ohm speakers (one per channel) is only going to give you about 300 watts per channel (approximately, and it varies between amplifier types).

However, if you connect two 8 ohm speakers per channel (a 4 ohm load), each channel will deliver its full 450 watts.

Ohm's Law says you should only get 225 watts at 8 ohms, but that's ignoring Total Harmonic Distortion, etc., upon which the 4 ohm rating is based.

This is one reason why people keep blowing their speaker drivers!