Here's a link to an article about using mono on the tower.
I would rate power handling for the M770s at 175 to 200 honest watts per speaker run in the highpass mode and if run flat. There is going to be a difference in real power between a strictly regulated and unregulated amplifier. If you have the factory pods containing the forward facing lamp, a percentage of these pods are not airtight, and if not, this would have to be corrected in order for the speaker to reach its max power handling without serious risk. Pay close attention to whether you are using the 'T' (air suspension) version or 'C' (IB) version in the correct application. A single JL Audio HD750/1 is perfect for four M770s. However, that is way too much power for a single pair. This amplifier is underrated and does not lose power with a drop in voltage supply.