Building PC! Advices please!?

You need a new power supply. 350W is not enough for any of that and more than likely doesn't even have a 6-pin PCI-E power connector. If you try and plug a graphics card in without one of those when it needs one, your computer won't even start up most of the time. 600W or better should suffice and give you some breathing room for extra components. Don't skimp on the power supply or you'll pay for it later. Get a good brand like Antec, OCZ, Corsair, etc. and make sure it's got 80% efficiency or better at least.