I'm working on a $1600 turn key nav solution (fitted.) for it but I do see your point.
for $1k you can get a decent box and if you have the screen already you are set.
as for DVB boxes,I tend to steer clear of the $100 boxes due to relaibility. as for reception - if you are in a clear area and city based (IE no buildings , valleys etc) then it works fine. I have customers that expect residential reception at 110kmh and its not really the case. too many variables really. terrain being one of them. yes its a LOT better than analog signals but it still drops out.
if you get one for nix plug it in and you will see what I mean . external antennas help but its still not as claimed.
if you feel like a chat my contact details are in my sig