I too have been looking at this, as I feel the car has poor damping characteristics (too much compression damping), and is sprung too softly.
The H&K kit requires alot of Maserati specific parts that may be hard to source in the USA, as well as $$$
I have looked into having custom shock built, but the company would need to measure the stock shocks, and they are currently on my car.
If someone has a used front and rear, it would help to bump start the upgrade.