Where are you taking training? Unless it is an advanced course, you probably won't need them.
Taking the 4 day practical rifle at Front Sight. They say they are recommended but not necessary. Their bays are all stone though, so I think I want some.
Anything Arc'teryx is awesome ^
If you do end up getting .mil pads, get the newer ones that look like turtle shells. The ACU ones that are kydex or whatever suck; they always end up around your ankles. Lots of guys in the Stan wear the pants with the knee-pro built in, seems to work for them. I didn't have them, so I can say, but all my guys are wearing them now.