Sorry for my delay in responding to you.
As far as Manheim values for a low mileage 2005 Maserati Coupe, for June 2007 the average price was $63K and for month to date in July it is $61K. But you have to keep in mind that these are dealer to dealer wholesale prices and transactions performed by dealers with experience & comfort in bidding on cars that they have only briefly been in contact with. They also have the connections to have work done on those cars to bring them up to retail level standards which comes at additional cost. So, unless you are a licensed dealer and are comfortable with everything that comes with those prices, you will probably spend alot of time looking and making lowball offers on cars and most sellers won't deal with you for very long. Afterall, if a seller is willing to sell his car at a price that wholesale dealers are purchasing at in auctions, why wouldn't he just trade it in for that and take the tax benefit on top of that.
In reality, for better or for worse, Maserati Coupes are in the US in such low volume that most traditional valuation guides like Kelly, Edmunds, etc. do not list them. Even the Manheim auctions have processed very few which is why the values change so much from month to month. Maserati's are not like Mercedes or other volume cars so it may be that only one or none went through the auction during any given period. For that reason I really believe that the best guide for individuals wanting to purchase one is looking at the current market prices. Go to cars.com or autotrader and see what prices are being asked for which models with what mileage. That is how I have priced mine which is pretty much at the bottom end of the 2005's which pretty much is the same as the top end of the 2004's and we all know the 2005 updates were pretty significant. The good news is that we all as Maserati owners in a way have much more control over how much value the cars hold so long as we stick to market level prices and don't just dump them because some dealer wants to make a quick buck.
I have put my car on ebay a couple of times, each time lowering the price or changing the structure of the auction. I actually had it sold the first time at $73K, but my buyer was in CA and was relying on not having to pay sales tax but when his credit union wanted to collect his portion of the funds, he found out he would have to pay sales tax and it took the car out of his price range. This was my fault because my auction originally stated that there was no sales tax for private sales in Arizona, but I don't think I was as clear about the Arizona part as I could have been. Now I make sure to say it 2 or 3 times.
I also decided to list it on ebay again today. This time I lowered the price and included the aftermarket wheels in the price with hopes that a serious buyer will take notice. I know from past experience that, in general, ebay lookers fall into two categories: they are either serious buyers or bottom fishing dreamers and most cars are basically auction quality and not as clean, documented, and low mile as mine. I am assuming that is why Gransports can have such a low price yet no one is willing to buy them because of something stated in the car history or title work. I have pretty much followed most of the interesting Maserati Coupes that get listed and the real ones are pretty consistent in price.
What I have found from my past ebay experiences (one car sold on ebay, 2 cars sold to people who saw the cars on ebay, and 1 car purchased from an ebay seller) is that most serious buyers will call you & get as much info as possible to research and make a decision on the car. Once they come out and see the car and meet the owner & see how meticulous and car crazy he is, it usually has worked (in my case) to solidify the purchase. I pretty much always have 3 to 4 cars and my attention span for each one of them usually lasts from 1-2 years so I spend alot of time observing and participating in the car market.
Regarding my suspension upgrade, I am not extremely technical in that area, but from my understanding of what the Ferarri technician told me is that the suspension is extremely similar to what the setup is on the Ferrari and that Ferrari has used it for a long time. Even with the Skyhook system, the suspension has a fully adjustable height set up and that is what was adjusted on my car along with all of the balancing and alignment that is required. The shop I took it to is Redline here in Scottsdale, AZ and the owner is extremely detailed and particular in the work he does which is almost exclusively on Ferrari and Porsches.
Again, thank you for your feedback. This thread should turn out to be really helpful for those looking to buy or sell Maserati's as well as current owners. I truly believe that my Maserati (and all Maserati's in general) delivers more than any other car out there for the same amount of money. They have a level of performance similar to that of BMW M and Mercedes AMG cars, but they offer so much more with the Italian bred performance, interior quality, & true level of exclusiveness due to low volume production. Seriously, I live in Scottsdale, Arizona where highend cars are a dime a dozen. You can pull up to any one of the numerous Starbucks here and see a parking lot full of AMG cars. But, everytime I drive my Maserati I get honks, smiles, thumbs-up, and calls from friends asking me did you just drive down Scottsdale Road. The car really stands out and that says alot when a car can do that in this town.