There is going to be sun glare on any screen you install that is visible to the driver.

You can cut down on the glare a few ways:
- dark window tint
- tilt the screen back at an angle
- recess the screen in your dash a bit
- lean your screen back at an angle

Unless you're willing to shell out the $600 for a Transflective touchscreen, you will have glare.
Hell, even the transflective screens have glare, but they're just brighter so they overcome the glare much better.