I just bought a lowish miles 12' Jetta Wagon TDi, the GPS is woefully inadequate as I spend several hours a day in my car driving 120+ miles. The market has a plethora of options, Amazon having several to choose from in the sub $300 range. Looking to see if anyone has any experience with the current offerings.
I'm looking at double din radios also so I'll tell you what I've learned so far.
Android Chinese radios. Pot luck may work may not... seems to be getting better and moving up in price. Basically a Android tablet radio.
Main stream double din radios. Various priced and seems like not much difference. Most have BT and can connect to your phone. Sound quality goes up in price as far as I know.
Android Auto the app. It lets you basically mirror your phone.
Look into a raspberry pi mini computer with crankshaft if you want a easy diy project.
Look into the RCD330G head units. They were originally equipped in China I believe for Volkswagen. Lots of successful swaps documented online with minimal fuss.