That PSU can handle that 3 cards ?
Looks like a 600watt, so no you're going to need to upgrade. I'd recommend a 1000-1200w PSU for 3 GPU's, especially if you plan to have other stuff connected (hard drives, dvd drive, fans etc).
I use a 750w hale90 for 4 gpus, using only maybe 350w or less (5870, 5830, 5830, 5770). This is going by a kill-a-watt thats measuring a known 650w 5 card rig with high end chipset/cpu and an inefficient 1 card rig, and the 4 card rig in question. draws 1150w total. yes thats 10 gpus with 1150w