The need for a subwoofer with 8-inch monitors would depend on the intended use of the system. If you are a music producer, a subwoofer can be essential for accurately hearing and producing low-end frequencies. If you are a gamer or home theater user, a subwoofer can enhance the experience by providing more impactful explosions and rumble. However, it is important to note that the overall sound quality, balance, and accuracy of your system will be affected by the subwoofer, so choose one that complements your monitors well. If you are using the system for critical listening or high-end mixing, you might want to opt for professional studio monitors with built-in subwoofers or a separate subwoofer that has a very low frequency response and high accuracy.