alpine type r upgrade

My amp is 1000w rms @ 1 ohm, so dual subs split power at 500 each. I have been looking at the new type R's (currently running 1 older R @ 700watts), which leaves me room for an amp upgrade as they take 1000rms each now. I have room for a maximum of a 4ft^3 box so i think the R's would go...