protection light always on?

Here are a number of thoughts:

Your speakers "run" at whatever the amplifier puts out, not the number printed on them.  If you have four speakers connected to a four-channel amp, they will each receive the same theoretical power output from the amp depending on their impedence.

You say your protection light is on with the vehicle off, is the Hed Unit off too?  If so, how is the amp getting power?  What did you use for the remote "on" signal?

A constant protection light generally means one of these things is wrong: 1) system power is too low (meaning your alternator and/or battery is overloaded or defective.) 2) speaker impedence is too low or a speaker lead is shorted out or shorted to ground. 3) an input (RCA) is shorted or grounded. 4) the input gain is too high. 5) the amp is bad. 6) the head unit is bad.

Try this.  First, fix the remote power on situation.  The amp(s) should receive a signal from the HU and only turn on when it does.  First, turn your gain all the way down.  If this clears the light you had it set incorrectly, you need to set it properly.  If it's still on, disconnect all four speakers from the amp.  If the protect light is still on, the speakers are OK, if it goes out the speakers or speaker wires are your problem.  Next disconnect the RCA's.  If the protect light is still on, the RCA's and your HU are OK, if it goes out one of these are your problem.  Also measure system voltage with a DMM at the amplifier and ensure you have 12volts or greater.  If your voltage is OK and nothing you do clears the light the amp is probably bad.

If you don't understand how to do what I suggest above, you will need to take the car to a car sudio shop and pay for some help.  Cheers.