I'm still trying to find a source for the old Kicker 6x9 sub's...but in my travels I found these.
http://www.tb-speaker.com/detail/0509/W69-1042.htm

I've heard mention of TB speakers a few times over the years but have never heard them myself.Favorable mentions by the way...

I'm just throwing this out there for consideration.I know alot of people that want more bass but don't want the hassle of a box and such...these might fit the bill for a few.
The 8 ohm rating would work well with a 4 channel amp too...