TechPowerUp published a review on the ASRock 4X4 BOX-7840U Barebones Mini-PC
A quote from the article:
The ASRock 4X4 BOX-7840U offers near-class-leading number-crunching capabilities while consuming less power than its direct competition. Additionally, it is easier to work on and upgrade, making it a well-rounded system for a home office, casual gaming, or emulation.ASRock 4X4 BOX-7840U Barebones Mini-PC Review