Hey Martyn, if that amp's 700W is rms power, then yes you can power 2 1000W subs. However if it's peak power rating, then you won't be able to maximize your listening enjoyment.
Hey Martyn, it'll depend on the amp. If the amp you have is 700W rms at 14.4v, then it's good enough. If it's just a peak, and you have cash, a stronger amp will definitely produce much desired result. Look for a 1 ohm stable amp since you have 2 subs. That way you can connect the subs in parallel mode (pos to pos and neg to get on each speaker, then joining all the pos together and all the negs together for 1 ohms). Oh another thing, look for amps with remote bass control. It is very very handy. I use it all the time.