No post on my homebuild. Could be cpu, mb, or psu. How do I find out which?

I've had my homebuilt for a few years now. But last month, I moved to italy and brought my cpu/heatsink, mobo, HD, graphics and sound cards with me in my carry-on luggage all kept inside anti-static bags.
I just finished reassembling my build yesterday incorporating new pieces (case, psu, etc.), but at the moment of truth the system did not post. the case fans all turn on as does a power light on the mobo, but no beeps from the case speaker. I tried a bench test with just the cpu and case speaker hooked onto the board, but when I powered it up, same story:lights and fans but no beeps. I first went to asus support (my mb is an m4a78 pro) and they suggested the bench test and then were ready to RMA the thing.
As far as I'm concerned the problem could be in a few places. It would seem just as possible to me that the cpu is damaged from the flight over as the MB. Not to mention I have this new PSU that I've never used before.
Is there any way I can check each piece to eliminate which is the source of the problem?

Once you are down to the core of your system - PSU, motherboard, and CPU, the only way to be certain is to either test each questionable part in another computer, or swap each part with a known good one.

unplug everything but the necessary for you to see it's working. to my own experience dusty RAM, IDE cables and poorly inserted power cable on motherboard are the culprits.