I highly recommend the Upper A. It's one of the best runs in Colorado especially if you do an overnighter with train support. Be sure your group has solid big water boating skills though. At 3600 cfs it is full on IV+. The stuff in between the V's gets big. I remember one nearly river wide hole when we ran it last year at 3600 cfs that caught me by surprise
. A guide can show you where the V's are but you'll proably be on your own for the stuff in between. Swimming the Upper A doesn't look fun. The water is freezing and the run is remote. We've chased boats a long ways at this level and have had many people take the train out at needleton after having enough on the upper section.
I don't mean to scare you off, just wanted to give you a heads up. If you're into big water class IV+/V- it's a great time especially if you run the lower box. Last year's run at this level was one of my favorite runs of the year. Just be ready for it at this level.