Garmin nuvi 500 Series Update

After several days of waiting for Garmin to answer an email request,
and also trudging around the web looking for answers, I finally did
the smart thing and went to my friend Steve, who has a Garmin. Steve
also was not sure about the nuvi 500 series (he owns another model)
and my questions not being general Garmin, but more model-specific, I
finally gave up and called Garmin. The lady I spoke to was helpful,
polite and well informed (however I did wait like 25 minutes to speak
with her--thank God for speaker phone!)

My questions were pretty simple.

Q: What is the difference between the Garmin Nuvi 500 and the Garmin Nuvi 550?
A: The 500 comes loaded with street maps of the lower 48 states, and
topographic maps of the same. The 550 comes with street maps of all
North America, but no topo.

Q: Can the Nuvi 500 and 550 provide a downloadable track log*?
A: Yes. This can be viewed and monkeyed with using the free
downloadable Mapsource software on Garmin's site.

Q: Can the topo maps of North America be added to the 550?
A: No.

Q: Can the topo maps of North America be added to an SD card and then
used in the 550?
A: Yes.

So I don't know still which to get. I will probably get the 550 just
because I might head up into Canada at some point just to use my
passport. ;o) Or should I get the 500 with the topo maps? I don't
even know (besides geocaching which sounds really cool) what I would
use topo GPS for.

*"The track log in a Garmin unit are points automatically stored when
you are moving. It is the electronic equivalent of laying down a
"breadcrumb trail" to mark your path. These points will be shown
strung together on the map page of your unit so you can see where you
have been."