I bought my system from
http://www.pugetsystems.com. (no relation). I did a lot of research and the company is tops at putting together a custom system from the best stock parts.
They also have excellent technical support (I think its for the life of the computer). I bought a system 3 years ago and they just helped me with an upgrade problem, getting knowlegable same day responses.
Email them or give them a call and they will help you configure a system. It will cost more than, say Dell (which makes very good computers). The big advantage of a custom computer is that they are very upgradeable. Most off-the-shelf systems have limited upgrade ability. I know this from experience.
I can not advise you in regards to laptops.
PM me if you want to discuss this further.