Gaming computers are high performance and are fairly expensive. Some even have liquid cooling to keep the temperatures low. Consider brand such as Alienware, Asus, MSI, NVidia, AMD, ATi, Intel.
You don’t have to buy the top model of everything, you can make small sacrifices, and improve performance by replacing your standard Hard Drive with an SSD drive with approx 530mbps+ Read/Seek time. For example, try using a brand called Silicon Power found on Amazon for approx £50. It easily outperforms brands such as Samsung, Crucial, Sandisk, and others.