We did the Gorge yesterday and had a ton of fun at 700. Still quite a few things that would trip up a true III boater though. We had more carnage at 700 (two swims from class IV paddlers, one we had to chase for a while...) than at 820 a few weeks ago. Then again it was like paddling chocolate milk with the runoff. Just my .02...
Another option is Parkdale (III-/III). I did it late September last year at 370, so I'd guess it would be a lot more fun now. It's a mellower option than the Gorge.
If you do Brown's at low water, I'd recommend putting in at Ruby Mtn rather than Fisherman's as you'll cut out the flat/rocky paddle in.