Could be the PCM, as it's job is to provide the ground for the coil packs.

Is the PCM power relay ok, if in doubt, swap it for the A/C power relay & see what happens.

But unless you did something to the PCM while messing with the speakers, it's likely ok.

Seeing as how you had the B- cable off, maybe the battery to chassis, or engine, ground is open.

So if you have a good set of jumper cables, parallel the B- connections between the battery post & engine & body, with the jumper cables on the batteries B- post, the other end connected to a unpainted bare metal spot on the engine & body & see what happens.

If it starts, remove one jumper cable at a time, to see which one kills the engine.

If no joy, look to the crank or cam sensors, as they tell the computer when to ground the coil packs for spark & squirt the fuel injectors.

Do you have a CEL lit????
If so, if you have, or can come by a scantool, hook it up & pull the trouble codes, as they can offer up good clues.

A bunch of thoughts for pondering, let us know what you find.