mmmmmm....legos.
Anyway, there are lots of these posts, and I have yet to find a resolution. One of the problems with coming here looking for this answer is that you are looking at the "HomeBuilt" forums. This means that people here actually build the computers themselves, after having bought all the parts themselves.
There are options like Alienware, Cyberpowerpc, pugetsystems. However, you just have to search the interwebs to find what exists, and then look for reviews to determine what you think is a good option.
Everyone here will say, "build it yourself."
However, if you do the research and produce a list of what is reputable, you can post it here for other people for reference.