Nothing you are claiming requires sophisticated equipment to test or confirm (the sub is either on or its not etc.) In fact, using test disks often only complicate things further. For example are you sure the test noise you used had low frequency information to redirect in the first place? Many test signals are heavily bandwidth limited.

That said, let's try and keep things as simple as possible. Run a digital output from a standard CD or DVD player, not your HTPC. Put in a Red book CD. Play the disk with your 990 set to stereo, mains set to "large" and sub set to L/R + Sub. Under those exact conditions I get bass output from my sub on both units. As I move the crossover point higher (say a quick jump between 40 and 200 Hz), the difference is significant.

AS for the condition of your unit, please email me (I've included this in each of my previous posts) the serial number and the name the unit was purchased under. I'm sure this was a new unit if that's what you ordered. Customs has been known to open units, but I'll also fully examine this.