Bluetooth amp on order, questioning how to wire 3 speakers?

Get a monoblock and jump off of the two channels as a high level input..lol

But really you need a four Channel amp and would essentially Bridge two of the channels for the center speaker to be mono. I worked at a stereo shop just before becoming a mechanic and did installs. You can't even run series off of that two channel because then you'll have one channel that's overloaded with two speakers from an impedance imbalance