4 subs 1 amp 600watts

I have 2 rockford fosgate r2d2's 10 inch subs and 2 cheapo subs old school style 1 600 watt sony explode amp with all 4 subs connected to the right channel only b/c i dont have a rca cable for the other channel. What is the worst thing that could happen putting 4 subs two sets with two...