Update

[Loud Ranger]

Lets say around 100

im always upgrading so i would get some thing that puts out 400w at 4 ohms but is 1 ohm stable so if you need more power down the road you wont need a new amp.

the amp i bought is an AQ1200d which does 1200 rms at 1ohm, 800 @ 2 ohms and 400 at 4 ohms, currently my sub handles 800w rms so i have it wired to 2 ohms, but if i wanna get louder i can add a second 2 ohm sub and get the full 1200w rms at 1 ohm.

if you plan to go bigger you might wanna spend a little more now rather than replacing things later

 

[Loud Ranger]

http://www.sonicelectronix.com/item_12210_Hifonics+BXi+1208D.html

this ones 200 but if you plan to go bigger you would have 1200rms on tap if you got a sub with a 1 ohm final load

this ones a little cheaper but doesnt have as much potential
http://www.sonicelectronix.com/item_17368_Rockford+Fosgate+PRIME+R500-1.html#