IMO, the only reason Qualls, Wheeler, and Backe would be "on the block" is probably because the Astros would have to give up something to get something. I don't think it's an indication of how the Astros feel about those players. If the Astros had it their way, they'd get Abreu (see the Astros reference on #3 of Stark's list) for Wandy and a couple of minor leaguers or something like that.
Frankly, I love all of the players that are currently projected for the Astro's 25-man roster, but I understand that if the Astros make a big trade this offseason, one or more are likely to be dealt. As much as I (and probably the Astros) would like to see Qualls and Backe remain on the team, trading them for Abreu (as Stark suggests) might not be a bad idea. Then again, I'm not Tim Purpura.