Kaptan,
In simple terms, two speakers of same impedance in series doubles the impedance and in parallel halves it. In your case, two Sony speakers in series 3 Ohms + 3 Ohms will make it 6 Ohms, which should be fine with your Pioneer. You can either use the combination as fronts, front highs or even surrounds.
Most importantly, your Sony speakers are 1 way and full range, so such a connection can be advised.
Though it is not very complicated, I would advise that you do a little more research, or even look for some more simpler articles on the topic in the net and go about it.
I do have an assortment of some bookshelves and even Sony 3 Ohms speakers and have tried various combinations in the past with great success. But again, PLEASE TRY only if you understand the concept well.
Best+