Without being overly direct, as I don't know the exact condition of your instrument, what I really meant to point out is that with falling interest in the older organs and a bad economy, it may be difficult to find an offer higher than $100 - 150, even for a spectacular theater organ. Shipping is probably not an option for your customer as well since it is many times the actual cost of the instrument. I sold an M103 for $80 last week and I had to advertise 3 times over a 10 month period to get just one serious customer. He lived about 30 miles away and had his own pick-up. At the same time I was able to secure a 3 manual Conn Theaterette about 10 miles away (for under $200) because I was the only local inquiry and had a friend with a pick up.
Regarding other collectibles, I'm not an expert, but have heard there are guide books for relative value. The value to an individual is certainly going to depend on how well the piece fits in to their buying strategy and any "memories" associated with the object. Watching similar items on Ebay is usually a good way to learn the market, but don't put all your calculations on one individual sale. Again, the buyer in that instance may have a special reason for going high.
Hope you enjoy your new home! I know you will miss your many treasures but you can be happy for those who acquire them.