i have two of the 530hcx
they are fantastic, i put the mini sd card in it, i have the topo maps washington, utah, idaho, montana , wyoming, nevada, oregon, colorado, and still plenty of room for more if need be
i use them for hunting but mainly for snowmobiling, great unit to have any time in the outdoors.
you can use them to pull your buddies position, which comes in handy when hunting or sledding.
you can send notes to each other as well, we have used that feature before when hunting and radio silence is a must with the bulls in close, worked really well.
530hcx gets my vote