2 ohm just means there is less resistance and therefore will draw more power out of your amp. i would still get a bigger amp than needed to provide the headroom for transient peaks and avoid signal clipping. if you were to run a smaller amp it wouldn't mean it will sound worse. it will just not be as loud or as clear at loud volumes as the signal gets clipped by the amp failing to produce the power needed.

as for speaker let your ears decide. can't go wrong with what sounds best!

prices for pillars i can't answer you'd have to ask shops near you.