Timetoownu

So i just got a new car. 2004 Trailblazer. I got a new head unit. Pioneer AVH-X2700BS . i got some cheap speakers for my doors and i put my old sub in for now. Its a Alpine Type R 10". Now i love my sub but i am wanting more. I am thinking about getting 2 12" Type R's and was wondering if i was to hook up my 1 10" as well would it make a difference? or would the 2 12's just over power the 10 and make no difference? I would buy another 10 but i am also trying to save some room. So any help here would be appreciated.