Im ordering a BL 15 with hyperpole option. Im deciding on a kicker 1000.1, would this amp be big enough for the bl 15? I know kicker underrates their amps so it will most likely be closer to 1200 rms. Or would a Sundown 1500d be more sufficient?

Sufficient is going to depend on the box and your listening tastes.

The rms rating is a thermal rating. Actual power that can be applied is going to be determined by the enclosure.

Also, there is no 'need' for a certain power level. You will not hurt it with lower power than the rms rating. It will perform with 500w or 1500w. Just depends on how loud you want it.

That amp will be sufficient. The sub's RMS is only 1000, remember. There is absolutely no NEED to overpower a sub. I've had 200 watts on my 1000 watt sub before and there was absolutely no difference except the loudness, as Adrian said. But then again, realize that there is a point of diminishing returns. You won't see the same output gain going from 1000 watts to 2000 watts on that sub compared to going from 200 to 400 watts.

zx series is rated @ 2ohm

kx series was rated @ 1ohm

remember this when deciding your voice coil configuration...

There is no such thing as underpowering, only overpowering. Just don't be stupid and you'll be just fine. No one has ever blown a speaker from too little power. Lots of dirty clipped power from an amp being raped and impeding the cooling motion of the moving assembly, yes. Killed by too little power, no.