I hate to break this news to you but it may not just be the mobo. The fact that you get no led signal form the keyboard may indicate either a bad mobo or CPU or both! Did you run this system overclocked?? what happened just prior to the system not powering on? Did you shut it down and then nada or did the system power off during operation? Bad smells emit if it powered down?
When you power up the system, does the cpu heat sinc continue to run? Is the hard drive spinning? I would pull everything off that mobo, reseat just the cpu wiht new thermal paste, cpu fan, one stick of memory and the video card (no other peripheral including the hard drive) and see if you get keyboard leds to blink and the preboot beep. Try that first before you start spending any money. If it will power on ten I will help you to check the voltages and potential ground voltage leaks from the mobo.
A dead system can be cause by a bad pheripheral device such as a sound card or even the video card if it is shorted. You can try the cpu and memory only boot (you will bet the one long two short beeps form the bios indicating that the video card is missing but if it will power on that id good news, Then you simply start adding stuff until the sytem fails to boot. OK?
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.