key word "basically"
Punisher : I guess not.
Yes, I made a comment that puts down this thread. But, it is in place. I'm sure nobody has heard 4 solo Xs and a Jackhammer, so basically this thread is pointless. Worth a few bad comments? Yes.
Anyone trying to speculate what will be louder is doing only that, speculating. The MTX jackhammer could be some GIANT spl sub that puts out crazy numbers, or it could be some weak sub that isn't capable of 140db in it's best box. Nobody knows, so this thread is pointless, and should be closed.
To answer the question, I personally would go for the 4 12'' Solo X.
And subs do not "do" watts, that is something you would typically refer to as an amplifier. Your Xplod does not "put out" 1600rms.