New amplified subwoofer installed but NO sound. Help Please.

[Rado]

Hello. I got one of those slim subs and hooked it in my 2001 X5. The problem is everything looks normal and connected and green light is on the sub but there is no sound from it at all.
Here is what i did so far:
-positive 12v to the box behind the spare tire
- negative to the bolt on chassis
- remote on to the white wire on the factory amp harness
- checked the high input wires to speakers and all phases are good
basically I followed this instructions:
http://www.xoutpost.com/electronics/...-included.html

I checked with a volt tester that there is 12V and remote on and ground working, just no sound.
Then I found this post:
http://www.xoutpost.com/articles/x5/...ctory-amp.html

and here he tapped into different wires for the speakers.
Should I do that wiring or the one on the top - I'm confused. Is there anything else I can check or do? Please Help.
The sub i got is from soundstorm lab, here is a link and there is a doc with the manual as well there: SOUND STORM | everything else is just noise

Thanks in advance for any help. I would like to get this working soon. I ordered it from amazon, so a replacement sub is on its way just in case this one is defective, but if the new one has the same problem, then something is wrong with my wiring.
Also I forgot to mention that i have the aftermarket hualingan radio unit and i'm very happy with it, since I bought it one year ago.