A9 and K9 are pretty weak, I only play those in late pos. But again, I'm not looking to play that many hands on hopes of a flush or straight, I usually don't hang around long enough to even find out if I'll make one or not. My limit game is a different story, of course.
I'm not sure that I see many reasons to play these 2 hands in a NL game. Again, that is going to totally depend on the players at your particular table. However, unless I'm in late position (and mostly only if I'm on the button with no raises behind me) will I even consider playing those 2 hands. I'm a little more liberal playing A9o than K9o though for the plain and simple fact that there are sooooo many people out there that will play any Ax. Again, that comes into play once I get a feel for the table. Unless I can limp in with these hands from late position they get folded without much thought or regret. If these cards are suited then I will play A9s for a limp in from most any position. I will still only play K9s from late position though and again, only if I can limp in with it.