The Black Cube Linear is a great product. It's a great addition to your home audio setup if you have expensive headphones that require amplification. Even if you don't, the Black Cube Linear will provide a noticeable boost in sound quality for cheaper headphones.

As a cheap way to increase the quality of your audio setup, the AT-HA20 is a reasonable alternative. However we would recommend saving your money and investing in a better amplifier later on, as the difference it will make and the scope for upgrading will be vastly increased.