@Poppageek if you consider the connections then the slot is rated 75watts and the 6pin is rated 75watts so that card has to use less than 150 watts...*3 =450watts for your cards plus your rig ???I would say No problem running 3 probably 4 if cpu is stock

Add to this I have a 1k-sr from pc p&c with 66amps on 12v rail and have run 5 cards (2*gx2+98gtx) + cpu @3.5 for months at a time where my maximum load according to my Kill-a-Watt clone is circa 850watts. The downside is that most PSU's are at their most efficient in the 50-60% loaded range.

@Huff..This last week on my main rig I have had to drop my shader overclock by 1 notch.....I'm not yet sure of the reason...rising ambients or different WU's but whichever the problem was not eue's rather computer lock-up without bsod or anything like that. Try a notch lower and watch the results