TimandSusan,
I too have used Street Atlas for many years (since 2004 and I have all of the upgrade disks to 2015). I think it is the best product available. I plan an RV trip on my portable PC in the comfort of home and then place the PC on the holder in the RV, plug in the GPS & Speaker connections (I use iTunes on the PC to play music), plug in the power and I'm ready to go.
Since there is no longer an update to Street Atlas, I purchased a Garmin for the RV and loaded BaseCamp (their 'trip planning' software) on my PC. BaseCamp (in my opinion) is difficult to use and is rudimentary compared to Street Atlas. S0 I sent an email to Garmin regarding their combining with Street Atlas and the reply for their technical staff was disappointing - to say the least. In a nutshell, their advice is to abandon Street Atlas and learn the Garmin way. They did indicate that if I wish to continue to use Street Atlas for planning, I could export the plan file as a ".gpx" file and then import that file to BaseCamp to complete the planning and transfer to the Garmin GPS unit. What a MESS!!
The Garmin RV GPS will not connect to the PC for display - which means my map is now 5 inches instead of 17 inches!! 5 inches is OK in for a driver in a car with the unit close, but in my RV, the display is quite a distance away!!
The Garmin unit is not cheap! and I'm not sure of a good way forward to be able to plan at home and then easily move the plan to the rig for the actual trip. Right now, I am planning to keep on using Street Atlas as in the past and hope that there may be sufficient negative feedback to Garmin that they will integrate Street Atlas capabilities with Garmin GPS and be able to present the trip progress on a portable PC. They have all of the software and it is a matter of getting them to 'talk' to one another. (Garmin maps are updated more frequently and in that regard are somewhat better than the Street Atlas. I use a Garmin unit in my car/SUV)