I use Acme Sound B2 2x10 three way speaker cabinets. I own four and all are 4Ω impedance. Using a stereo power amp that is stable at 2Ω per channel, as most pro ones are, I can drive all four at once should I need to. As a statement of fact ALL of my amplifiers are happy driving into 2Ω loads.
The difference between an amplifier designed for 4Ω loads and one for 2Ω loads is very little.