If I were you I'd go for a PSU around the 500w mark (less would also be fine) and I'd stick with good brands like Corsair, Seasonic, Tagan, etc.
If I were you I'd go with this motherboard and get the 9600GT. Ofc if you want wifi, you could get a cheap £10ish wireless PCI card.
For cases it's really down to want you like - the Antec 300/900 and the Coolermaster 690 are both highly respected cases.