Computer for gaming purposes

Technology-wise, most things that are well-known are not only over-priced, but also don't give you the most bang for the buck. One example being Alienware. (I'd say Apple, but it's really not a gaming computer.) Custom computers typically will be expensive too, but it's the benefit of creating a beast of a computer as well as an excellent end result. Not to mention that it basically allows you to customize your computer to your liking.

Well assembled pc will be somewhat less expensive then a branded pc and also you will have option to customize it to suit your needs. You can decide which processor you want, which motherboard will be good one, how much RAM you need, which graphics card to select, which screen you want, etc. So assembling will be a good option.

If you're going for mainstream games that you play on Console and want to play them on PC instead, you should probably build your own, most computers can do some games, but they can't play all of them at high settings.