sonotube at 115db

I'm new at diy audio so I figured sonotube was the best way to start, i'm looking for a good 115 db spl from listening position, tuned to 20-25 hz, i'm thinking 2 12" woofers and i've tried using winISD but I can't make much of it, so let's just say i'm starting with 24" sonotube cut to about 4-5ft. Can anyone help me with sub, amp and port recommendations to get what i'm looking for at $700 or so? Also, I might be able to get a big discount on mtx equipment thanks to a friend, so if it was mtx equipment that would be real peachy. Thanks in advance.