My nuvi 500 was stolen...

[marquito]

I had enjoyed my Nuvi 500.  I had created several maps with help from google earth and basecamp but I figured out the drawbacks of the nuvi 500 real quick.  I couldn't upload a map overlay or tracks from either google earth or basecamp (and I really tried).  I had to use the poi every little bit to make a trail and follow that.  Once I followed it a track would be created but this was not ideal.  I had made several maps I like and tried to load them and only the poi would show.
I enjoyed tinkering with making the maps, trails and overlays even though I couldn't load them on the nuvi 500. 
I like the oregon 300 or 400 but before I get it I want to know that its going to do everything I want it to.  (highly customizable)   I use it for ATV/UTV trail riding and I would also like to load city navigator on it for the road.  The reviews would like you to believe that they can all do anything you would like it to.
If anyone has any suggestions for the right GPS I would appreciate it.   These things are not cheap and I would hate to buy another one and find that it doesn't do what i want.   I'll find and load the maps it needs (City nav, topo) thats part of the fun.  I just need to know its going to do what I want.

[Boyd]

The Oregon 300 and 400t (there is no such thing as a 400, just 400t) are old models and I haven't seen anyone selling them new for awhile. The 450 is the replacement and there is a $50 rebate on it through the end of Sep. You just missed the REI sale where you could have gotten an Oregon 450 for $200. Current price at REI is $275 (including rebate). I have the older Oregon 400t and have really enjoyed it, but the screen just isn't very good on the older models. The 450 has an improved screen and better compass.

Recently I got a Montana 600 and really like it - best Garmin GPS I have ever owned. The screen is spectacular, larger and brighter than any of the Oregons, with more pixels. It also has a number of advanced features not present on the Oregon or any other Garmin models (such as "shortcuts" that are macro's you can create to automate complex functions). If you can afford the Montana, I think you would be happier with it - if for no other reason than the better screen.

All of the Oregon series can use "custom maps" (.kmz files) that you create yourself. The Oregon is limited to 100 tiles per map but the Montana supports 500 tiles per map. Both Oregons and Montanas also support Garmin Birdseye subscriptions (satellite imagery and scanned USGS 24k topo maps). There are a number of programs that can assist with this, but Garmin has a simple tutorial that works fine for small projects: http://www8.garmin.com/outdoor/custommaps_instruct.pdf

All Garmin units support vector based maps - even your Nuvi 500 - so you can make these regardless of what you get. Mapwel is probably the most user-friendly program for making this kind of map: http://mapwel.eu/

Most mapmakers on this site are using cgpsmapper along with other tools to make maps that are compatible with all garmin models. See the tutorials for detailed instructions: http://www.gpsfiledepot.com/tutorials/how-to-create-garmin-topo-maps/

But as for your original question: yes the Oregon 300 and 400t would support any kind of maps you want, but I would suggest the Oregon 450 since it's the current model. If "highly customizable" is the most important thing however, nothing else comes close to the Montana.

[marquito]

Thanks for the info! 
The Montana sounds obviously better.  I just don't know if it's $150 better than the 450 or not.  The bigger screen would def be a plus. 

[Boyd]

If possible, I would try to find a store that carries both. REI or maybe Cabela's?

[Seldom]

Doesn't the Montana provide spoken turn by turn directions?  If so, it would fully substitute for a Nuvi as well as being a handheld.  (Maybe worth $150 to keep your eyes on the road with CityNav rather than the GPSr.)

[Boyd]

Yes, the Montana will give you spoken directions with a routable map. There's an auto mount that includes a built-in speaker, or you could use the audio output jack and connect to your car stereo.

[Seldom]

But if it only has an external speaker it sounds like it wouldn't tell you to "turn right on South Kaibab Trail" when hiking.  Is that correct?

[Boyd]

There's no built-in speaker. So you would need to use earphones, or some kind of small external speaker if you wanted voice directions while hiking. Personally I can't think of anything more annoying than a talking GPS when I'm out on the trail though. 

[trapperrick]

  That's a bummer that your nuvi 500 was stolen. I've had one since 2009 and love it. I use it on my ATV and I download the tracks on different trips on Mapscourse and BaseCamp on a map that I downloaded from here. It does have it's shortcomings though and as Boyd mentioned, the new Montana 600 is quite incredible. I'm holding off for another year or so because the advances in the GPS units in just the last 2 years is incredible!