I've got the desk dock (from Verizon) for my Maxx. It came with two clear plastic adapters...one for the Razr and one for the Razr Maxx. Without the adapter, you may be able to leave a case on. The HDMI and micro USB ports are a tight fit...but they do work and the dock options that are enabled are nice.
I decided not to get the car dock. Instead, I got the Mountek CD Slot Mount MT5000-C from Amazon for 20 bucks. No built in headphone or power hookups, but it works great! Hope that helps.