OK, I played around with all different combinations tonight, and all showed up properly in my GPS.
Regarding the different types of downloads, if you go to the actual waymark page you can get a full gpx, loc, or kml. If you go to a list of waymarks by any method of your choice, that's where you can get a gpx lite. At any rate, all three types show up properly as a waymark in GSAK, as you can see below. They just contain different amounts of data. The first two and third two were imported by gpx lite, the second two by full gpx, and last one by loc.
Here are some screencaps showing how they look on my DeLorme.
GSAK version 7.6.1.x does not support sending of data (geocaches or waymarks) to DeLorme GPS', so that very well could be why it's not working. This was a very new feature first introduced Sept 20 and is still in beta testing, so you'll need at least 7.6.2.16. This beta version
can be downloaded by anyone, but you have to go to the forums on the GSAK site in order to get it. I've been using it for a month now, and I haven't had a problem with it, so it appears stable. Here's the
link to the thread. Scroll all the way to the last post of the second page for the most recent build. Hope this helps!