I should also recount the experience I had with State Farm and the appraisal/valuation. At first they offered me the standard "by the book" value of $7500. When I told them that was unacceptable based on mileage, condition, maintenance and mods they came back at $8600. Luckily I have an appraisal clause in my SF policy that allows me to hire an independent appraiser, and have them work with a SF appraiser and come to a mutually agreeable figure.
well long story short, it took me a couple weeks of hounding the shade tree appraiser I found, but they ended up giving me $16k for the car. I sent both appraisers a list of mods (totaling over $10k spent) as well as maintenance ($20k) I had performed on the car during ownership.
Side note: the SF appraiser was actually a third party company and the guy I talked to was very cool. He told me that basically after depreciation you can generally expect to recover 30-40% of the cost of mods spent on a car. So the $10k I spent yielded roughly an additional $3-4K onto the value. He said for maintenance it is not so black and white, but generally you get a much smaller percentage back. Neither of them wanted any actual receipts which I thought was kind of weird.
Another thing I did was send them listings of all the high priced ZHPs all over the country (avoiding geographic price bias) which I think helped. Ultimately my appraiser had my value range from $15.5k-19k which I thought was pretty high. Obviously I was happy with the final number.
I hope this info may prove useful.
--Wes--
04 330i ZHP Oxford Green/Natural Brown
04 330Ci ZHP Silvergrey/Alcantara (RIP)