Something doesn't look right... they don't look HDR at all.
I have tons of HDR from Moab and Grand Canyon, and you should be getting all the way up to "screaming red" on the dirt colors. The ones you posted look very dull and desaturated, must be something you are doing in the software.
Send me a PM if you would like to see some of my HDRs of canyon landscapes.
I can also try doing one for you, if you send me some RAWs.
When I shoot HDR landscapes, I shoot 8-10 exposures in 1/3 stop increments. But then I only usually only use 3 raws for an HDR - 4 at the most. It is critical to use the "best" exposures to get the "look". Especially when you see a sunset or sunrise, I go way under exposed, to get saturated colors in the sky. In your example, the sky is blown out. And all the foreground canyon is too dark. Do you have any raws that are more overexposed and more underexposed. You might want to try using those in Photomatix and see if you get more tonal ranges.
here is an image I was processing today that has a sunset in in, see how much detail I can eek out of the colors in the sky...
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