Thanks for your response Jim.  I tried to put everything into one outlet, but the wicked hum continued.  I'm a bad musician, but even worse electrician.  I ended up just rewiring everything - I removed the USB and added a midi cable to the Tascam.  Everything seems to be fine now.  

OK, I worked on this most of this afternoon.
 
1)  I tried multiple USB cables - no change
2)  I plugged everything into one power strip - no change
3)  I plugged everything into a second power strip - no change
4)  I took a spare computer and plugged the Tascam and FA-08 into that - no change
 
The noise always remained.
 
I found some oddities, though.  I don't even have to have my computer plugged into the wall to hear the noise - as long as both the Tascam and Keyboard are plugged in USB, I hear it - whether or not the computer is actually plugged into anything.
 
If I unplug the TRS cables from the Tascam, the noise goes away as well (which I guess would make sense)?
 
Now, all that being said, I wonder if this is actually an issue.  For me to hear the noise, I have to jack the line out of the Tascam way up, as well as turn the JBLs up as well.  Maybe this is one of those "it is what it is" things, and it shouldn't really matter.
 
Thoughts?