What is wrong with a sub?

David, very few speakers do deep bass well. Those that do have what amounts to a built in sub. So, many of us add dedicated subwoofers to our systems to get the bottom octaves. I love my subwoofers. There is no way I could get realistic bass without them. I would think at my age I am anything but a bush leaguer. Enjoy your bass and your system subwoofer and all.  

1+ wolf_garcia. mkgus as long as you keep it symmetrical you will be ok.
If you use two subs up front they should be identical. If you were to add two more subs they could be from a different manufacturer. The DSP is great but you have to know what you are doing and to do this you need to be able to measure the situation with a calibrated mic. You can not change the nodes in the room. You can only correct the frequency response at your listening position. If the listening position is in a nul point
you want to move it back and forth a little in the room to where the bass is if anything too loud. In a nul point it will cost you a lot of power to correct. This is easy to do. Get a test record or download with frequency tones. Play a 40-60 Hz tone and walk back in forth in the room right between and 90 degrees from the speaker axis. You will hear the bass come and go as you walk in just a few feet! Mark the spot you like and move the listening position to it. Now correcting the response will save you power and you won't need a 2000 watt amp.