I use a Garmin nuvi 885t with a RAM Mount on the dash. I like having the GPS receiver in my driving field of view.
I used a RAM Mount round plate with 1" ball, part RAM-B-202U. The base is 2.5" round and fits into the dash-top cup holder on the left side of instrument of the instrument cluster. I used a 2.5" adhesive disk to affix the base to the bottom of the cup holder. To the base plate I added a RAM Mount 6" arm, RAM-B-201U-C. To the arm I attached a RAM Mount diamond plate (plastic) with 1" ball, RAP-B-238U. The final piece is the RAM Mount Gamin nuvi 800 series cradle, RAM-HOL-GA30U. I will post pictures when I get my Sprinter back from Sportsmobile in a couple weeks. Sportsmobile installed a Titan III GPS antenna on the roof of my Sprinter, but the nuvi 885t worked very well without an external antenna. The nuvi 885t has bluetooth and MSN Direct features, which I use frequently. My peeves with this unit are few, the main one is that the max volume of the dual internal speakers is marginal when road/wind noise is high. This is my fourth Garmin GPS receiver and definitely my favorite.
Brian