General Punto mk2 rear speakers

[Doovydoo]

heeey. i have a 2001 mk2 punto. I have put in a new HU (Sony GT100) and a sub woofer with amp. i currently have the amp running of the back of the HU (rca jacks) and the sub off the amp.

I have noticed i have grills in the back for extra speakers. I would like to know the size of the speakers that fit in there pleaaaaase! and could anyone recommend some good ones plze too.

also how would i wire them up? there are no more outputs from the amp or HU (i dont think anyway). or could i just splice them onto the speaker wires?

thanks!