Building my own PC for the first time

[Chemical]

Hello,

Just as the thread title implies I am planning to build myself a PC in very near future considering that my old PC died on me and I cant use a laptop for proper gaming. Anyways, I would appreciate any advice, hints, tips and links that you guys can provide me so I can build a better PC for a lower price without blowing myself up or destroying expensive parts.

My main goal is to build a PC capable of running all current games on at least High setting and be able to play games several years into the future. 

Here are some specific details:

Budget: 600$-800$

I already have all necessary accessories I just need to build the tower.

Any case that works, I could care less about "cool" looking cases.

Motherboard: PCI-express 2.0 slot(1 or 2, preferrably two) , in the end all I really need from the motherboard is to be able to support all other parts and not constrict my future upgrades: I hated in the past having to buy a new PC just because my motherboard could not fit more ram or support better video cards.

CPU: from what I have heard CPUs dont need to be that powerful since most games dont use that much processing power.

RAM: at least two gigs, I would like to know how big the difference is between DDR2 and DDR3

Video Card: I think any good 512mb PCI-express 2.0 card for a reasonable price would work

Power supply: I have no idea here, need advice

Any other parts that I can not think of at the moment.

I will later on edit my post to show the parts that I am thinking of using for my PC for feedback. Thank you in advance.