Too BIG...
The Lowrance 500C is a great unit for an RV or maybe a big truck. I owned one for about 6 weeks before selling it and getting a Garmin Quest 2 (not for my Prius as it has built-in NAV.0
In my opinion, the 500C takes up too much of the windshield if it's attached to the window with the suction cup attachment that comes with the unit. More importantly, it will drive you crazy as it vibrates at the slightest bump due to both the long arm that attaches it to the window and probably also because of the weight of the unit.
If you get yourself a weighted dashboard mount, it might NOT vibrate as much, but it will still take up a lot of dashboard real estate. After a short time, you will find it's so big you probably won't want to go to the trouble of setting it up. Also, you have the problem of where to hide a unit this big. You certainly don't want to leave in on the window when your car is parked unless you want to put in an insurance claim when it's stolen.
If you have your mind made up on the Lowrance, I think you should at least consider the Lowrance 350C. The only question I would have about this unit is that I think you have to load different areas of the country via your PC as it doesn't hold the whole US as the 500C does.
Re the MP3 player that comes with the unit, it's a piece of crap unless you hook it up to your car sound system.
Just my opinion...
