Problem with just putting the top 6 ranked teams in the playoffs is it completely annihilates any prestige in winning your own division, which I'd not like to see.
Sure, you'll always get teams like the ones in the NFC East and South getting screwed over by an ultra tough division, but generally if they're good enough to really challenge they'll make the playoffs anyway.
I could see an arguement for having homefield advantage for the wild-card round determined by record. i.e The Ravens finish 11-5 and get a wildcard spot, Denver finished 9-7 and wins the division. Ravens getting home advantage makes sense. But you have to make the division titles worth something IMO, even if the division is weak that year.
Looking at Arizona's schedule though, they've not beaten anyone really any good except Dallas. Denver, as s**** as they've played in some games, have at least beaten some good teams in Tampa, New Orleans, Atlanta and the Jets. Assuming they don't make a royal mess of it from here, they'll be just worth their playoff spot.
I really dread what could happen against Manning and the Colts though... bad, bad memories...