Wired in series, that amp should have no issues driving 4 pair, but its pushing a lot with too chnls at 1.33 nominal impedance. During normal listening, this 1.33 will actually drop lower. This should put any 2 ohm stable amp into protect mode.

If the amp actually delivers its advertised 4 ohm and 2 ohm output, then I would suggest rewiring the 2 pairs of polks, to series. You will likely not have a noticeable drop in volume, but may actually pick up some sound quality at the higher impedance.