I would highly recommend the Garmin 60CX.
Full colour screen and totally portable......come with car kit but can also use with 2 AA which then last around 15-20 hrs.
Pix up minimum 6 or 7 satelites and is very quick. I use mine with City Navigator 6 and also take it hiking. Fully waterproof as well.......can get them for around $800 these days + car kit which includes charger, bracket etc for around $50. Well worth it IMO.......