I'm brand new to CO and looking for IV-V creeks (not super hero stuff) to run this season. I'm excited to boat CO after years in WA. Send me a private message if you want to get together.
Don't discount CA though. If you can swing it, a road trip there is well worth the effort. Here are a couple things I ran that were super fun and manageable for a reasonably skilled boater (I am NOT a super hero boater by any stretch):
South Silver: Despite being very steep, everything is straight forward and you can walk anything you don't like. We ran it at a solid medium flow and I wasn't terrified, in fact I wish I had spend a few days running laps. I imagine at high flows it can be very scary but most folks run it low to medium. Check out www.dreamflows.com
. The webmaster Chris is a very cool S. African transplant and he can be talked into leading you down if you're friendly over the phone. It's a guaranteed great time, kind of like a kayakers version of a Disneyland ride, while still demanding the respect that all rivers do. I boated it with a CO boater who compared it to a steeper, longer OBJ, although I haven't done that yet so this is just heresay.
Middle Fork Feather, 3 Day: One of the best trips I've ever been on! 3 Days of IV-V in a beautiful canyon. It steps up each day, so you have time to work up to the bigger rapids on day 3. You can walk most drops you don't like, although there is one at the end that is pretty much mandatory. It turned out to be quite fun though. The scenery, whitewater and camping are all top notch. Highly recommended!
The upper Yuba drainage has a number of IV+ to "reasonable" V runs that are really fun as well.
All of these rivers are within a few hours of each other. Pick up the Holbeck/Stanley Guide to the Best Rivers of CA. It's been around a couple of decades and is still the bible.
In fact, if you're considering CA, I'm interested!