not loud

I just got a new amp Kenwood Excelon KAC-X10D (http://www.crutchfield.com/S-MifNw0Z1YnE/cgi-bin/ProdView.asp?g=120&I=113KACX10D) and hooked it up to my sub that I have had for like a year, which is a pioneer TSW306DVC. I expected this to be loud 600 watts rms (amp) powering my 400 watts rms sub. So after I installed everything I set the input sensitivity to 5 volts (what my stereo puts out) and it was quiet so om my head unit I turned the bass all the way up and my sub level all the way up. Even with all of the I still can hardly here it over my other speakers. I dont have the optional Wired Bass Boost Remote but I didn't think I would need it. So can someone help me is it my sub , has it lost it's loudness over the year that I have had it (It was hooked up to a pioneer that only gave it 240 watts rms but I remember it being louder on the pioneer)? Has anyone else had this problem I would really like to know why it isn't loud. Thank you

it's in a sealed box btw

what impedance does your new amp make its max power at?   What impedance is your woofer?   how is it wired?2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR

2007 USACI World Champion

2007 World Record

2006 USACI Finals 2nd Place