I used the mentioned wattage calculator and I was up to 330w on a 300w ps. The generic one had 6 molex connectors and if I added any more (with a Y) I was afraid of overloading it. So yesterday I bought the thermaltake 420w pure power. It was not the one I was wanting to buy but the assortment at the store was getting a little thin with xmas and all. Hooked it up and its quiet (quieter than I thought it would be after reading the reviews) and works excellent. It has 9 molex connectors and heavy and LONG wires so I am happy so far. It seems to stabilize the temp in my case as well with the extra fan on the bottom. Just my two cents.