The problem I have with going after the big ones is that for the most part they're in the trophy waters and those waters are PACKED.
I'll hit up the South Platte a few times a year, during the week, and I'll always pull in a couple of 18-24"ers while I'm down there, as long as the flows aren't too low. But, I just can't deal with the crowds. I fish to get away from that shit.
This coming summer, I really have to do some digging and see if I can't find some decent remote stream fishing in CO. I haven't found anything within a couple of hours, that's for sure.