You're starting to get it
oHms, are a measure of resistance. Most subs are either 4o or dual 4o voice coils, meaning they have either 4o (for a single 4o voice coil) or 2/8o (dual 4o voice coil) of resistance. NOW, amps are made to put out a x amount of power at xohms. For the example lets say 400w(rms) @ 4ohms.
So you have:
amp--400w(rms) @ 4o
sub (lets say 4o)
Speakers*6@4o each.
there's 2 ways to wire multiple voice coils--series and parallel, one will drop your resistance in half, one will double it.
6speakers*4o=24o OR 2/3o This makes wiring it up to a 4ohm amp impossible.
Your best bet is to add a 4 channel AND a 2 channel amp to get 6 speaker sound.
Now I'm going to tell you that 6 speakers will sound like dog shit rattling around in a coffee can (the aluminum style can)
Spend all that money that you would've spent on a 4 channel and a 2 channel and 6 speakers, and put it into 2 GOOD components for the front and a 2 channel A/B class amp to power them. Stereo imaging, when done correctly, uses 2 front speakers positioned correctly to create a proper soundstage. If you want me to babble on more just let me know