dells ur best bet, altho u can only use dell parts with it for ur average joe that will probs just buy another one in 5 yrs time they have a good reputation for being reliable as far as i know.

building ur own is always gunna be better cos u can make it to ur own needs but for the some1 that doesnt want the hassle of building one then ur better off gettin one that use quality componants rather then a cheap high spec one that uses shite which will break in a few weeks.