The number 1 pick probably wouldn't net much because other than Clowney, there's no one worth trading up for.
Well, in general picks don't get traded regardless of situation at the top of the draft anyway. I was commenting more on the "value" part than actual trading. If Clowney's truly the one elite, sure-fire next Julius Peppers, a team may be offering 2 1sts, 2nd, 3rd and the Texans would still probably reject that.