Did you check out GarcianSmith's thread? It offers pretty solid advice.
I got this PSU, and it's working nicely: http://www.komplett.ie/k/ki.aspx?sku=339898
Higher wattage isn't needed really, at least if you're going with the HD5770, which I would recommend; it runs most games very nicely, only starts to struggle with bad ports or insanely demanding games, and it uses less power than my HD4890. If for some reason you do want higher wattage anyway, I would suggest you stick to Corsair. They do make great PSU's.
Also, make sure that you get a case that is right for you. Preferebly one with easy access to the Hard Drive Disks and toolless operation and dust filters. A good case can have a longer lifespan than all of your other components put together, so don't gimp out on it.
Oh, and here's Garcian's The gaming PC Upgrading/building thread
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