I use one of the handheld Lowrance models, it is the only unit that has an SD card memory slot that holds enough topo data for the entire east coast. It is way more advanced that any of the garmin products when it comes to topo data and landmark data. It has everything down to trails, and I find most of the data is very accurate. Most models come with TopoUSA so you can download any section of the country you need. If you are looking for good topos I would choose any of the newer Ifinder models that fit your budget (stay away from the older models they are not as good) Then buy yourself a 1Gig SD card and have fun filling it up with data.
I have the IFinder Fish (non color)
What I love
1) the SD Card SLot
2) waterproof
3) topo resolution is awesome
4) address search feature rocks
5) point of interest search is kick butt!! you can find the closest autoparts store, or restaurant with full address and phone number listing so you can call!!
6) it is pretty portable, larger than a garmen but the screen is bigger than most other units
7) 6 CD Topo USA install give you the freedom to download any section of the country without having to buy additional maps!!! look at the other units they almost always make you buy additional stuff, or they only hold a few quads, with one gig of storage I can hold almost the entire east coast in my hand
8) comes with 12v cig adapter for your car, and I use mine all the time in the car on a mount
9) the back lighting is clear and even, the screen is just impressive for a gray scale unit, and the color one is even better
10) dual processors makes the screen keep up with all the topo data
What I don't like
1) Battery life is a little short, I only get about 12 hours on rechargeable batteries
2) I wish it was a little smaller, but it's not a show stopper for me, I can handle the size, and frankly I wouldn't want the screen to be any smaller.
3) unit is made for land based navigation not turn based navigation. so if you looking for turn by turn directions this is not the unit for you. personally for me it's not a negative I just wanted to put it out there.
I looked around a long time for a good topo based unit, that could hold a lot of data and trails. Make sure you read the fine print, many garmin units only have about 8 to 32 megs of storage, that is not enough for more than a few quads. This is where the Lowrance really shines with the SD slot you can have very large portions of the country with full POI details.