upgrade my sound!!

I see the logic.  4 subs, one for each corner of the room.  Right now, that might be a bridge to far for me.  I’ll start with 2 and see how it goes.  Do you recommend all subs be of the same manufacturer?

The logic is a little different than you think. The most important factor is not the sub or its power or even how deep it goes. So no they do not need to all be the same manufacturer. Mine aren't even all the same design. Two are sealed, two ported, one isobaric! They work great because the main thing is lots of subs in lots of different locations creates lots of different peaks and valleys that all together result in real nice smooth bass. 

The effect is so powerful we had a guy with two sets of ordinary 2-way speakers trying to get the most out of them. I said take the two that sound the worst, put them on the floor pointed at the wall, throw a blanket over the tweeter so you don't hear that. He was amazed to find the bass response far better than he ever imagined it could be.

Not saying use small subs but am saying you can forget all the usual BS about how important it is that they be big or powerful or EQ or any of that. With subs how many is far more important than which one. 

Two or more subs, but NOT in the corners.