Great drives in Rockies & Utah... in August...

With a trip from Texas to Monterey and another trip from Monterey to Texas (hopefully following a different path), I need to do some route planning. The goal is to find roads that are fun to drive, but still get me across the states with reasonable efficiency... to find that, I need some local expertise on western Colorado, Wyoming, Utah, and New Mexico...

New Mexico:
I know I40... just lotsa dull straight slab. (Just did that back from Vegas.)
How about I10... is it just as dull? Looks worse on the maps, actually.
Any good alternatives?
How is US60?
Any great side-trips off I40 to break things up?

Colorado/Wyoming:
I know I70... eastern boring; middle great; western moderate.
Is there a good alternative for the western half of I70?
How is US40 from Steamboat west to Utah? Looks boring.
How is I80 through Wyoming? Worth the major trip to the north?
How about the trek 191 north to 44/43 to I80 for just the westernmost Wyoming?
I know many great side-trips in central Colorado; a few listed below.
Any great side-trips in western Colorado? Or in southern Wyoming?
Feel free to suggest other side-trips that make general east-west progress.

Utah:
How's I80? Better or worse than I70?
How's US40? Better or worse than I70?
How's I15 from I70 to I80? (I15 is pretty fun from I70 to Vegas.)
Is there a better way to jump from I70 to I80??
How's US6 from I70 through Price to I15?
How's US6 west of I15?
Any great side-trips? I hear Utah12 near Bryce Canyon is awesome.
How's Utah24 from I70 thru Hanksville over to Utah12? Make sense?
And then from Utah12 at US89? Take 89 south to Mount Carmel Junction and then west to I15??


Thanks!
(BTW, this is related to this larger thread in General.)