I would gladly take a SF, but I just don't seem them that often. I know they can be had on ebay, but I'd much rather prefer to see one pop up locally so I can try it out before I buy it. There was a '77 on Chicago craigslist not too long ago, but I haven't seen it recently.
I was pretty impressed with the DRRI when I checked it out. No, it doesn't have the mojo of a vintage amp, but I still thought it sounded really nice.