I am also wondering about: ALGA PRIMA AN 510 A, because it is only 5 inches and this size in a passenger car is the most comfortable. What you need is a fast processor and navigation framework, simple menus and Alga has it. Look at the speed of catching Fix (satellites), and what I mentioned earlier, updates (probably free - but I will not cut my finger). You can upload your own maps. For example, TOM TOM AND GARMIN are going on Linux and their own maps, they are good but for Germany, and you often drive around narrow streets (fast route) I checked myself. And a different price. Fact TOM TOM has a cool traffic assistant. Give it up on Vordona - crap, I mean the pale colors and there is a lot of poop on a sunny day! It's best if you find something with a matte matrix. I recommend you to read - The best navigation 2016-2017.
That's it for now.