I noticed that it has two slots for a 6-pin connector, but my current PSU (Storm LPK19 -- 35 700w) only has one 6-pin connector.
The AMD website says "500W (or greater) power supply with one 75W 6-pin PCI Express power connector recommended" which is great, but I've seen people posting on firums saying they have problems with only using one connector.
you can use two 4 pin molex to 6 pin pcie but its not recommended
its better to have a power supply that offers multiple pcie power cables
you probably have an old power supply so it would not hurt to upgrade it to something newer and power efficient
as for brand get Antec or Corsair power supplies as they are good reliable brands...550-650watts recommended for a single card
alvine took the words right out of my mouth. BTW, absolutely do not, ever, think you're getting a good deal by buying a cheap PSU. Cheap PSUs are a risk, not an investment. They will break, and best case scenario is that it just stops working, but typically they can take something down with them (motherboard?) or the whole computer if (it has happened) they catch on fire. I'm not lying to you, I saw it happen - I was there when a buddy's PC caught on fire - and it was his cheap PSU! I was there!
As a excellent minimum, I'd recommend this: http://www.newegg.com/Product/Product.aspx?Item=N82E168... (sorry, I know it's not a UK site but that's the model I'd suggest - if you can, make sure you get the v2 model of that, the site you showed us only carries -I assume- the original version).
Best case scenario, this PSU lasts a couple months then falls over dead. Worst case, it burns down your house. Do not buy it. If you've already bought it, throw it away and buy a new one. I'm dead serious, you do not want that PSU anywhere near your computer.
Just think about things for a second. You're looking at a $25, 700W power supply. This is about half the cost of what a 400W power supply should cost, but offers almost twice the power? How do you think they managed that? By cutting literally every corner.
If this thing actually provides 700W of usable power, I'll eat my hat. More likely, you'd see enormous power fluctuations (can damage your other components, by the way), lots of noise and ripple, voltage outside tolerances and an efficiency that would make you weep in sorrow.
Plus, looking at the product page throws up a ton of other red flags. A PSU that lists CPU socket compatibility? The two have absolutely nothing to do with each other, it would be like buying snow tires and the salesman assuring you that the tires will work fine with your car's oil. You'd get right up and walk out of that shop, because something's very wrong.
There's more, too. Claiming a "large" exhaust fan when the standard size is used? Listing a power switch as a feature? Claiming PCI support (again, refer to that snow tire analogy)?
Of course, we it doesn't list the power of each rail, either. This is usually an indicator that the manufacturer was deceptive and cranked up the voltage on the 3.3v and 5v rails to increase overall power, but not in any way that's useful to the user. Your power hungry components all draw from the 12v rail, so cheap PSUs can inflate their power output by dumping more power on the other rails that won't be stressed as much, allowing them to use cheaper components. Of course, when you actually ask the PSU for its rated wattage, it can't cope and usually dies quite swiftly (days to hours is common with really cheap ones like this, a few months is the best you could hope for).