September, October and into November are fun times to run Royal Gorge. Never in my seven years in Colorado has it been too low to paddle - it goes at 269 (my personal low), and there's very rarely less than 350 in there. (Sunshine is nasty at that flow).
The only thing that keeps Royal G from being a year-rounder is the possibility of major ice bridges in December, January and February.
It's really the same story on Gore. That run is honestly very fun at 450. You just have to watch for major ice in the middle of winter.
Bailey is at a great water level right now. I ran that into September last year. It's still fun as low as 200.
The Parkdale section of the Ark has some decent play spots when the flow is in the 300s, and it almost never drops below that. Usually it doesn't ice over. So you can do a nine-mile run with some decent play in December and January.
I ran Brown's Canyon in the 300s a couple times in January of 09, and that was reasonably fun.
When all that is iced over, head a couple more hours south to Taos and run the Racecourse section in January. Some nice little surf waves in there at low flow, and it is pretty much year-round.