Re: how stong do my psu need to be
That system would pull around 300W max at 100% load. You'd ben fine with a quality 450W PSU. You'd want 500W+ though with more than 30A on the 12V rails for future upgradability.
The Corsair is more than enough.
AMD Phenom II X4 955 BE @ 4.0GHz + TU120E lapped - MSI 770-CD45 AM3 - 2x2GB OCZ DDR3 1333MHz - Sapphire HD 4870 - Samsung Spinpoint 500GB 7200RPM 16MB cache HDD - Tagan TG600-BZ Piperock - (Currently open test bed) - Windows Vista Home Premium 64bit.