I was SOOO tempted to trade my GK 1001RB-II for one of those. Still might. You're not making it easier for me, man! I tried that in GC... I hate Markbass heads on Markbass cabs, but when I put it on an Ampeg 410 it was butter.
I love my GK, but it's not the lightest thing in the world. Like you said, the F1 fits easily in a gig back (or even in my hardshell case) and makes things so much easier.
Let me know how it works on the Avatar, I have the same cab. If it's gravy, I might give it another look.