If the gears are a big selling point for you, and you decide against the RT because you can add those later, you should know that at least as of right now, 4x4 models can't go larger than the factory 3.92 I believe. If the interior is the selling point, for that price, I bet you could find a Sport model around...maybe even a brand new one that hasn't sold yet you could get a really good deal on.
I had an 07 QC and I think had the dealership had an RT on the lot when I bought my 12 a few months ago, I would've gotten one. Ultimately, I'm probably glad I didn't just because of the room. My thinking at the time was "We have a car if we need to go somewhere as a family." But, I'm 6'3" and I like my subs so a reg cab might not have been my best choice. If you just want and RT and the other models don't appeal to you, I say go for it. Like I said, I probably would've bought one. I think you could definitely talk them down from $25,000, though.