do you think that the CyberPower Black Pearl is a good computer here i will put the link here http://www.cyberpowerpc.com/system/CyberPower_Black_Pearl/
Yes, it will play those games well. I'll link the article review for the Radeon HD 7870 with the GTA 4 benchmark (read through performance on other games too). Minecraft isn't too stressfull and the Black Pearl surpasses the optimal recommendations of minecraftwiki.net http://www.tomshardware.com/reviews/radeon-hd-7870-review-benchmark,3148-11.html
http://www.minecraftwiki.net/wiki/Hardware_requirements