It's like trading a Ford Pinto for an Audi A8.
1. The audio improvements are very great and noticeable. The AV7000 only supports Dolby Pro Logic; however, the BS1 supports Dolby Digital and DTS.
2. The BS1 has excellent video processing, line-doubling, and 1080i support. I always thought that the AV7000's attempts at improving video did far more harm than good. The AV7000 only uses composite video and the colors become horribly bright.
3. There are far more inputs on the BS1 to allow connecting more video devices.
4. The BS1 provides far greater Beo4/Beo5 control of non-B&O devices including Blu-Ray, HD DVD, Apple TV and many others. B&O stopped updating the AV7000 code-conversion a very long time ago. By now, most of the code-conversion of the AV7000 is obsolete or incomplete and frustrating at best.
Keep in mind that the new Beosystem 3 offers even greater audio/video/control improvements than the Beosystem 1.