What should i get?

I sold my ruger p89 and Hi point 9mm, would it be a waste to take the 400.00 and buy the walther p22? What is the difference in stopping power?

As of now i am between the walther p22 with laser, Smith and wesson sigma .40 a glock 22 or a 5906, any recommendations?

IMHO the Walther would be a very poor choice for a lot of reasons.
The triggers suck, I've heard of people having feeding problems, and it has very little stopping power. If you want a gun for self defense then don't get a .22LR. A 22LR just doesn't have the penetration and energy to even compare it to a 9mm. Many will say it would work, and I am sure it does work with good placement, but why get one if you're also considering a 9mm?

Of your options I would get the Glock 22. The 5906 or Sigma wouldn't be bad choices at all. Sigmas do have heavy triggers though.

My suggestion is go to a range that rents guns and rent a few.
There's nothing worse than buying a gun only to find out you dont like it.

are you using your pistol as ccw ?

stopping power : .40S&W > 9mm > .22LR

.22LR is fun to shoot but under power as a SD round. :)

have you try out the S&W Sigma .40 and Glock 22 at the range ? if you can handle the recoil of .40 and shoot well it's recommended to get either S&W Sigma .40 or Glock 22. if not get the S&W 5906. :)

As a primary SD gun, I would stay away from 22lr and go w/ a more effective caliber....of your choices, I'd probably go w/ a G22