Well, I researched mainly in-dash systems, but came across some nice sites for hand-held / portable units:

http://www.gpsresource.com/

http://www.epinions.com/auto-Navigation_Systems-All

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".