In general though, if your amp produces twice the power into 4 Ohms as it does in 8 Ohms, you should be in good shape for an 8 Ohm rated speaker. That will give you plenty of current overhead, regardless of the phase angle. Do note most amplifiers can't do this but do come close.
EPDR more important than impedance alone
That's Equivalent Peak Dissipation Resistance.
Info here: https://www.audiosciencereview.com/forum/index.php?threads/stereophile-has-started-calculating-epdr.15497/
(Don't be put off by ASR!)
Info here: https://www.audiosciencereview.com/forum/index.php?threads/stereophile-has-started-calculating-epdr.15497/
(Don't be put off by ASR!)