its a PW-15S 15inch 400rms dual 4 Ohm (DVC) sub I prefer a mono amp with 2 channels or 4 channels, but how do I wire the sub is it better to bridge or not.

with this sub thread, you can get 2 or 8ohms at the amp and here are _configurations.asp diagrams http://www.the12volt.com/caraudio/woofer?

basicly i want to know how many watts the amp should be, The rms on the sub is 900 watts, the amp i want is a hifonics brutus amp it says @ 2 ohms 900 watts, does that mean it will give the sub 900 watss if the sub is 2 ohms???
Also should i put it ina ported box or sealed....
please help me out

you will need an amp that puts out close to or right above 900 rms for peak performance. but what amp to get all depends on what the ohm load of the sub is and what voice coil it is. if its 4 ohm dvc then you will want an amp that can give you 900 rms @ 2ohm. if its 2 ohm dvc then you'll need an amp that puts out 900 watts rms @ 1ohm. so check to see if the sub is svc or dvc and then check the ohm of the sub. you can repost another question with those specs and we can better help you out. i can also tell you kicker, jl audio, rockford fosgate, and jbl are good brands to look for