That's not how amps and subs work.
Amplifiers put out power, into subwoofers. The only things that amplifiers care about are their supply voltage, gain, and the resistance they're seeing from your subs(because with more resistance, less current is able to pass through subs). So, regardless of your subs' RMS ratings, that amp will always put out 1kW at two ohms as long as its gain is set correctly, and it's getting the correct voltage.
So, that means that because your 4 ohm subs(which are 350W RMS a piece, 700W RMS as a pair) can be wired to 2 ohms, they'll be seeing a possible 1kW. You can set your gain lower so that they'll be seeing less, so that would be fine.
You aren't able to post links with so few posts. To get a link in your post, you'll have to hit the edit button and then add it.