Looking for decent gaming PC

I'm planning to get a new gaming desktop.

I want the price range to be around $500-800

I need some suggestions if possible, thus far the best pc I found would be this : Here

This PC seems to be pretty decent except that it has 4GB RAM, I feel that for 600 I should be getting atleast 6GB +

What do you guys think?

Also, would this PC be the better choice although it's a little more pricey. Here

 

Both systems are good, but the more expensive system is really up to date with USB3. The less expensive system is better bang for your buck, but if you can afford it, and it isn't a hardship, the more expensive system will keep you satisfied longer.