Reputable gaming pc site?

I have an around ~1400 budget. I want to buy a gaming computer that can run most games on at least medium settings. I was found one at alienware.com but looked around and read reviews saying it was overpriced. I then visited cyberpowerpc.com and found a $650 that was waaaayyy to good. I m a sceptical person (one of the reasons im not religious) and it seems like there was something wrong. Does any one know any reputable sites that sell gaming pcs and preferably lets you customize them (i can live without this though)