Ric,
I will agree Dunn is a better option than Lee or Soriano. But the other two only cost money (and maybe a 1st round pick in 07). Dunn would cost alot in proven pitchers (in the ML or in the minors).
The Astros are already potentially losing their #2 and #3 starting pitching, and you are suggesting they trade away their #4 (Hirsh) a potential #5 (Buchholz) and their best young closer type RP (Qualls), for Dunn. I am not sure I can swallow that much for the benefits Dunn gives you over Lee or Soriano.
If all things were equal Dunn would be my #1 choice and for the right deal he still would be, but not for a deal like you suggested (or said you would do). Not when someone close to the same middle of the order production like Lee is also available at a similar cost.
I doubt the Astros pay Lee more than $13 per year, if that. He (as others have pointed out) isn't in Berkman class to get the $15 Mil type contract. Not to mention if he really wants to play in Houston, let's see the home town discount. I would like to see them land him for $11-12 per year, which is pretty much in-line with what he is worth.