I'm glad that you weren't hurt. Insurance companies have procedures that they follow when assessing property damage accidents. This is the reason that someone told you that they will need three estimates before they'll make you an offer. Don't worry about having to tow it to different places-- the insurer will have to have the adjusters visit the car where it is. Take the time now to sit down and make a list of all of the after-market stuff on the car. If you have saved receipts from the purchase of this stuff, get them together. If not, get on the internet and print off current prices of the stuff, making sure that what you're printing is exactly the same model. List when the after market upgrades were made. Having all of this together and organized will help speed things along. It may also help for you to get back to the place where the car was towed and get photos of the most expensive after market accessories so there isn't any fight about whether they were on the car.
Usually I tell people not to give a recorded statement until they've spoken with a lawyer. The problem in your case is that it will be hard for you to justify the cost of hiring a lawyer with only a property damage accident. When you give your statement, make sure that you stick to what you saw, heard, and know. Don't guess about things you didn't see. Be very careful when estimating speed, distance and time. Answering "I don't know" is absolutely fine if it's true. Good luck.