Ignore the 'nominal' ohm figure. There no such thing as 4 ohm speakers because impedance changes depending on frequency. Most good amps are designed to play 4 to 16 ohms.
They're easy to drive compared to some other speakers advertised as 6 or 8 ohms nominal.
My Dali opticons are advertised as 4 ohm nominal but they don't drop below 4 ohms. They are 4 to 11.5 depending on the frequency. The 11.5ohms is around 70 hz.
Here is an impedence curve:
View attachment 1666378
You can get 8 ohm nominally rated speakers that drop to below 4 ohms.
Are you looking to have 2 pairs of speakers?