What is failing when MBP does not boot up AT ALL?

Hello,

The last time I used the laptop was using it on battery until it was low. Then subsequently, I closed the cover and went to sleep.

It never woke up again.

It exhibits symptoms of a completely dead computer.

When I press and hold the power button, there is no chime, no spinning sounds (from HDD or CD drive), the sleep/power light does not illuminate or blink, etc.

The battery does appear to charge (using an 85W power adapter, the LED would turn from green to amber, then back to green when fully charged).

The power level indictor (small round button on the left side of MBP) does appear to work and is showing the level of power on the battery.

I brought it to the Genius Bar and they could not determine a fault (brought it to the back room, checked serial number, and then determined that they would bill me $100 labor + $210 parts if I decide to have it sent in)

Here are the things I have tried (from research and from Matt from ifixit's advice) and with no success:

1. resetting SMC (unplug battery, press and hold power button) - I do not hear any chimes/sound from that.

2. resetting the PRAM - doesn't really work as it appears to require the computer to at least power up.

3. removing / reinstalling RAM (tried to boot with different number of pieces of RAM).

4. boot with/without a battery, with/without power adapter.

What should I try next?

1. boot up HDD on friend's non-unibody MBP?

2. troubleshoot wiring connections?

What's the next in line that could fail and exhibit these symptoms?

1. completely dead logic board?

2. completely dead HDD?

3. bad battery to logic board connection?

4. My guess is that this is not a graphics card issue since it primarily affected the nVidia 8x00M cards. Is that correct?

Thanks.