brake machining

[blackers10]

hey guys
i have slotted rotors on the front of my AU series 1 fairlane
and they are warped(steering wheel shudders from side to side under medium braking and at SLOW speeds under brakes it pulsates as the warped portions of the disc roll thru the brake calipers im guessing)

i was wondering if these can be machined as they are slotted?

and also is it worth upgrading to AU2 brakes to avoid warping all the damn time as ive heard AU 1s suffer from this very often
and if i get AU2 upgrade will i need new discs?
what other options are there for upgrading to? that have multi pot calipers and larger discs(i have 18" wheels so space is not an issue)