Don't look now but the Texans D just got a whole lot better with the addition of CB Johnathan Joseph and S Daniel Manning. Rumors had them being in the mix for Nnamdi Asomugha but this option might make more sense for a team that needs big-time help in the secondary at both CB and Safety. We'll see if the defense can improve to the point where this team finally becomes a legitimate contender under the guidance of Wade Phillips and the institution of a 3-4 defense that will feature Mario Williams as an OLB. Should be interesting.
Houston has had a horrible secondary the last couple of years. I have to imagine what they have done is an improvement over that. Those two players combined might have come cheaper than Asomugha anyhow and he can't be everywhere at once.
With the number of teams running a 3-4 defense now I imagine sooner or later the advantage of finding good players will shift dramatically in favor of teams running a 4-3 if for nothing else than good linebackers that play well in a 4-3 will be a lot easier to find than ever before. (I think years ago when Belichick started going to the 3-4 and started the trend we see now it was partially because almost everybody was running a 4-3 and it was just a lot easier to find good linebackers for a 3-4 with not as much competition for them.)
I could also again state that finding a top of the line nose tackle for a 3-4 with is one of the biggest needs for it is always pretty hard.