Need help picking amp

I have two 10 inch harmony Audubon subwoofers. Each of them are 250 rms and they came with a 400 watt amp. I believe that amp has blown and I was wanting to upgrade the whole system. Could I get a 1200 watt skar amp to run my harmony audio subs until I get 2 500 watt skar subwoofers or should I just upgrade the whole system at once?