I've spoken to Auto Acoustics about a stealth sub box for an A4 avant B5 and they have said they would be interested in making one for the b5 avant if i can get enough people interested. Apparently it costs them about £2000 to get the tooling made up but the quality is very good. The current one for the saloon version costs about £189 ish and is made of fibreglass and mdf with all the baffling and wiring points ready to just attach your sub. If seriously interested could you let me know, we need about 8-10 people and obviously there will be a lot of input to get it as flush as possible to be able to use all of your estates boots space. Intention would be to use the rear cubby holes without damaging any of the factory trim and would be much flusher than the saloon version as you have more side space to work with. Thanks.