Did you install all of the motherboard standoffs (studs) into the back of the case before installing the motherboard? Could be something shorting out. I would breadboard it for testing, meaning taking the motherboard out of the case, putting it on a non-conductive surface (wood, cardboard) and try to see if it boots up properly. If the cable to the front panel is long enough you can try powering it up using the case's front panel power button, or you can touch the two power-on pins on the motherboard with a screwdriver for a second to power it on.
Edit: the extra wires coming from the front panel may be USB connections, which go to a different spot on the motherboard, so I wouldn't worry about them for now.