i have the enermax etl1000ewt-m and it have 6 pcie plug
i'm at 940-960W at the wall plug actually with 5 GPU, each of my gpu are using about 100W in afterburner. not sure what else is using the 450W missing... i have only a celeron 2820 on it and i don't use it to mine..
Not sure if i can plug another GPU on it :s
http://www.oldi.ru/upload/resaiz_images_catalog/big/102/1027706/0428001_11.jpg
thanks =)
I would strongly recommend against it. The VRAMS in gpu consume power too and they add up. Anyway it is always advisable to run your PSU at 80% capacity for best efficiency and for give it some room for accommodating spikes. By adding one more GPU your rig will go over 1000w and will lead to power shutdown by the PSU, though there are protection circuits I am note sure your's have one. So please dont add more to it.
Regards,
BLife