Yes, the Synology DS1621+ can be used as a multimedia server. Here are a few key points that make it suitable for this purpose:

- Performance: The DS1621+ is equipped with an AMD Ryzen V1500B quad-core 2.2 GHz processor, which offers sufficient performance to handle multimedia streams without transcoding, especialmente if you use direct play.

- Storage capacity: It has six storage bays and can be expanded to 16 bays with two DX517 expansion units, providing ample storage capacity for your multimedia files.

- Multimedia applications: The DS1621+ supports various multimedia applications, including Video Station, Photo Station, and Audio Station, as well as integration with iTunes Server. It can also function as a Plex server, especially if you don't need frequent transcoding.

- Connectivity: It offers several connectivity options, including Gigabit LAN, USB 3.0, and eSATA ports, as well as the option of adding a 10GbE network card to improve transfer speeds.

In short, the DS1621+ is a robust, high-performance media server solution capable of handling your media storage and delivery needs.