Debian is usually very slow to implement new release applications. They are usually two or three versions back compared to other distros. This is due to Debian's priority of stable operation of their operating system. Debian may not utilize Xfce 4.8 for another couple years.

It's strange that your Settings Manager looks just like the version in 4.8, though. It's different in my 4.6 in Slackware, as shown in that screenshot above.

I'm stumped, my friend.

No,Debian stable only receives bug fixes and security updates for existing packages,not newer package versions.
You *might* find Xfce 4.8 is in Debian Backports at some point:

http://backports.debian.org/

This is one reason why many Debian users use Testing or Unstable.

I'll take a guess that "Testing" is more stable than "Unstable".

Are there any Live images of "Testing" somewhere that I can at least try out to see if it will load/run?

There is the Debian live project,but it doesn't appear to be using Wheezy yet.Worth a look anyway:

http://live.debian.net/

As regards to Testing and Unstable both can be fairly stable most of the time.
There will be lots of packages entering Unstable at the moment after the release of Squeeze,so there is the potential for more bugs/problems than normal.
Lots of people run Unstable without problems,so don't let that put you off.

This is taken from the following:

http://www.debian.org/doc/FAQ/ch-ftparchives#s-testing

Packages filter down into Testing once they have been in Unstable for a period of time and have no significant bug reports against them.
For more Testing information see here:

http://www.debian.org/devel/testing

Which is right for you? I don't know,your call.