I have an RD Alpha D2 that will get really loud off 1000rms. It was upgraded basically to a AlphaMax before RD started making them. if your interested LMK
I definitely recommend a custom sub. I love my sub! Sounds really good in the 3ft³ @ 31 hz box I have in it and the lowwwws are awesome!
SPLaudio does great work and has great customer service! He sent me pictures throughout the whole build of how the sub was coming and I am definitely pleased with it. I'm not even powering it all the way and it still gets loud! Send him a PM and he may be able to build something for you.
Plus you also get the joy of being able to tell your friends you have a custom sub //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif