If you like Navi then go for the
AVN2454
I like the idea of a double din unit. it looks like factory and infact is pretty much the same unit as a factory navigation with more features. But wait til the 5 volt preout version comes out if you plan on going with an external amp.
Both of those units you had shown arevery nice as well. Keep in mind you will be well above what you wanted to spend once you've added navigation to the alpine and kenwood units. Another very good option is the
Pioneer Avic N1
These go for about 1500 on ebay, also there is supposed to be a replacement coming out soon, the N2.
The eclipse unit will be about 200 bucks more than the pioneer. Both will be much cheaper than adding navigation.