I think that if the channels are bridged to 2, the impedance of the speakers would likely be outside of the specifications for the amp. The amp is rated for 1.5ohms to 4 ohms @ 75wx4, but 3 ohms to 8 ohms bridged. Assuming the speakers are connected in parallel, this would lead to a 2 ohm impedance per channel which would be two low for the 4 channels. Would it work this way? Maybe would for a while, but it would eventually lead to failure. If they were run in series, you would be fine (8 ohms impedance), but the amp would produce less power.
Others may disagree with this, but I would probably hook a speaker up to each channel of the amp.