Glad to hear you say this since your tastes are the closest to mine I've ever seen. Now what do you mean by the back speakers don't work? You only get sound from the sub? It's likely just a wiring problem if so. The subs in these things aren't crossed over so based on the impedance of the sub you could wire the back box or fix the wiring in parallel or series etc. If you want I could help you with this.

Is the sub in this the standard 8"? And is it 4 or 8 ohms? (usually says on the speaker).