That kinda sucks, your options are 0.67 ohm or 2.67 ohm. And since you only need 900 rms, you need a ~700 rms amp to run below 1 ohm or an amp that puts out around 1300-1500 at 2 ohm to give you a solid 1000 at 2.67 ohm.
I say get a Kicker ZX1500.1, that way you can run three at 2.67 and if you want four you can run all 4 at 2 ohm. Just set the gains correctly (conservatively).