I've heard the Mira 2 and Brio 3. Even though the specs don't scream out major differences, the Mira has noticeably more grunt, which translates to a greater sense of ease, as well as more resolution. That, combined with the remote control and somewhat better build quality, makes it more than worth the extra money to me. On the other hand, the Brio, particularly the latest version, is a very, very good amp with an excellent phono section. If your speakers are small and efficient, and you don't need a remote and don't mind cheaper-feeling volume control and input selection switches, you can put the extra money toward sources.
http://www.positive-feedback.com/Issue28/rega_brio.htm
http://www.positive-feedback.com/Issue28/rega_brio.htm