The best way to figure out whether it will work would be to calculate the current draw on each power rail and see if the total is within the max limits of your PSU.
Your Xenarc is rated at <8W @ 12V, so it will draw (8W/12V) = 0.67 amps on your 12V line.
Look up the specs on everything you need to power and add them up. Hard drives and Optical drives usually have their power draws listed on them, but for the rest you'll have to dig up the data sheets. Motherboard power ratings get tricky, because their max power draw virtually never happens. The Intel D201GLY2 mobo I'm using is rated at over 180W total, but that is assuming the PCI card is drawing the max allowed current, and that all 6 USB ports are fully loaded as well. I've been told the D201GLY2 doesn't go over 40W, so I feel good about using an M2 for it plus all my peripherals.