Cut a long story short, I have become slightly addicted to repairing my own phone after apple keep trying to rob me in full d...
I would hazard a guess at the connectors, the home button is #2 connector if my memory serves me right, I would hazard a guess at the home button being #5 as U can't think of anywhere else that the power button would connect to the logic board, unless of course it's the camera connection? I would play it safe and strip it apart and just make sure they are connected properly.
Might be worth taking the front off again, hold down #1 connector with your thumb and try turning on your phone again, these connections are well known for being a bit sensitive.
If you look on the connector ribbon itself there is a part number, I can't remember what number goes with which but I had the exact same problem when I replaced mine, I was sent a 3GS part when I ordered a 3G part, took me a while to figure out where I was going wrong. Don't take the fact that you have ordered a certain part at face value.