I already said this before but I find TT5 with an Ipaq 1940 adequate. I use the bluetooth receiver as I hate wires and the batteries are good for 4-6 hrs. Not sure 'bout the scenic but mounting central to dash work fine with good signals and quick start up.
One tip though.
If turn u off the POI's the display scrolls a lot smoother.
POI Edit is also a very useful little piece of software for updating the gatso locations, mcdonalds locations, etc etc etc.
Sorry but I have a fetish for Mc D deli sandwiches.. mmmm...
Oh and yes you can orientate the screen at 90 degrees which gives you the same area as one of those all in one go packages..
I use the tom tom car kit / mount with no probs.