I have been in the I.T industry for 13 years now as a I.T technician. I repair all brands, makes and models of PC's including self built PC's. I work for a company that is the warranty and service providers for all the major brands so I get to see what happens behind the scenes. I am factory trained in DELL, HP, Acer, Asus as well as factory trained in printers.
If you want a brand name PC then look no further than a DELL. You order what you want on line and it gets delivered to your door. If you want one made up then go to a dealer that specializes in gaming PC's and get them to assemble one for you.
Buy the most up spec unit you can afford at the time and remember this unit is for you not every one else. Why get something that you wont use because someone else told you that you should have it. I see people with entry level units that have had no issues for over 5 years. I.T equipment has a shelf life of 3 - 4 years after that they are dinosaurs. they age in dog years.
Once you know what you want in a PC then the next most important aspect when choosing one is the warranty. Dont buy a extended warranty unless it is the manufactures warranty. DELL are the only ones that will come to you within 24 hours of you making a call and fix it for you in front of you weather you are at home or at work. NO OTHER manufacturer will do this. HP is not worth the hassell and their warranty is SHIT. ACER warranty is even worse.
Hope this helps you out mate.