Line Array 15" SUBS

[voodooless]

My budget is small because I think that spending hugh amounts is not a guaranty to a good sound.
But I can buy for some 5000 dollars over some years, I prefer to go step by step.

Given this, two huge columns of 15" woofers might not be the very best of approaches either

Also note that anything more than one sub will be sub-optimal (pun intended), because it only has a single subwoofer output. If you have sub amps with DSP included, this would work much better already.