Everything has its pro's and con's... Read reviews on ResellerRatings or similar and you should find somewhere that you feel comfortable ordering from.
One place will offer up a great system, but you will be sacrificing support, service, etc... In the end, you get what you pay for in one way or another.
However, I will admit that I was surprised that cyberpowerpc did have some decent reviews despite what I have heard personally from past customers of theirs. Look into them like NosBoost recommended.