any one know any good 2din navigation systems 4 an 03 ml 350. or anyways to make the sound sound a lot better without wasting a lot of money.

The only way to cheap Navi is those sit on top units like Tom-Tom, Garmin, etc....

There's the add-on in dash kit made by Alpine for Mercedes-Benz which is the same as the factory installed unit
Part# is BQ6820821 , it's $1200 which is less than the aftermarket Alpine that is not MB specific.
Remember that the Mercedes one integrates nicely with the sound sytem and tele-aid, lowering the music while it dictates directions.

I agree with you that the in-dash setup is much nicer but theres no cheap way to get it.