The 21"er is gone...I just have a pair of original 10" Assassins that I'll be running off a 4 channel(not sure which configuration of 4 channel amps I'll use, but I have three at the moment, all around the same 4x100 power). 4ft^3 at 30hz is the plan, but I might do 28hz like the last box I had for them.
In all honesty, horns are 99% not going to happen. I'm about to get some of those TB 3" bamboo fullranges that a few people were praisig at
diyma. Since I'll have my midranges and tweets aiming right at me, paper cone mids and soft dome tweets will be my friend I think. I tried those mids in the photo above, which are made of aluminum and magnesium, and they'e just too bright diretly on axis...I like a more laid back sound.