Yes you could buy another NA101e and hook one 12 to each amp......that would give you 500rms@4 ohm each sub......To wire this all you have to do is run another + from ur distro to the amp and ground it...as well as the remote wire and if the amps do have an output run a set of RCAs from the main amp output to the new amps input..........If the amps are high in cost I would say just go buy a new amp that does 1000RMS@2 ohms.
EDIT
If they are DVCs 4ohms you cannot run 4 ohm per sub to a channel u must be running 8 ohms or 2 ohm......So in this situation buying another amp will do nothing because the amps are only 4 ohm stable bridged and you have to run 2 ohms bridged.
So you options if I read correctly are to run both of them at 4 ohms bridged to one amp or to go buy an amp that is 1 ohm stable....or 4 ohm but finding 1000rms 1 ohm is easier.........
Look into a refurbed viper1200.1 or a Orion 1200d amp they will do 1200RMS@1 ohm for u and refurbed on ikesound is like 189-209 usd.........
I hope I helped you out.....Also if it helps tell us exactly how the wiring off the subs is...to the amp.
Jay
Wait I just looked at the subs....they are Dual Voice Coils right??If so wire them up to acheive a 4 ohm loud and run the bridged on the amp that will give you 500RMS to both subs.