A Mac will give less problems and runs about a hundred times better than a Win PC. Go look first as Mac's are different but if you go PC look around and find someone that builds if your going above $1200 as you can put one together that will outrun a cookie cutter. Under 1200 go with what ever you want but HP is OK but stay away from Dell.

The real difference between building one and buying one off the shelf is the quality of the components for the same price. Friend of mine builds them as a second biz so if you want to PM me what your price / specs are I can see what is out there.