Sad news that you are planning to sell it, seems such a shame after all you've done.
Just had a look at the advert and some serious kit frankly , but as much as I hope you get the asking price I don't think you will unless there is a buyer that really wants it at the price.
Highly tuned and modified cars and A4 B7's are no exception don't sell very well , its not that they are not worth it but more a case of buyers are very wary of used modded cars and what would happen in the event of a mechanical failure, it would be a much more costly repair in its current state of tune with all the mods than if it were just factory level with maybe just a remap, and at the end of the day its resale value will allways be the book price plus a bit for condition etc....the modded parts have very little effect on its current market value , if anything it makes it harder to sell as only a small group of enthuiasts will be looking for such a car.
Anyway its a shame to see you sell it and I doubt your company car will be as much fun.
good luck
rob