Professional gamers
You ever used an SLI setup? That might be better now but alot of the time they are buggy or just dont work.
What about that thing where you pay a subscription and all the computing is done on the other end and you just play. Gamefly or something?
Buying from curry or comet will land you in the same boat tbh. They always cheap out of their mobo, hdd and ram as they arent attention grabbing specs like quad core or X ghz.
Some are bad some are good. I bought a Dell for about £300 (Was about £700 (base unit only) but bro worked at PC World and it was discontinued then discounted for staff), then upgraded the graphics card, took my old sound card & hard drive over and upped the RAM to the max. Old pc custom built motherboard died and couldn't be arsed with the cost of making another.
£ for £ a built pc will ALWAYS be better. The mobo would have been a low spec one. Generic cooler, slow hdd and so on. They will charge for the name, customer support and the cost of someone putting it together and building it.
Unless your getting a mad pc like one of the top of the line scan ones you will be better off with a diy build. Graphics isnt a massive thing to me so with that money I saved i got an SSD so it can be tailor made to budget and use.
But horses for courses.