there is some validity to the room response/node, etc. i wouldnt put two different subs in pair to correct this though. the idea is to get a uniform sound, which you will not get from two different subs. i dont typically get into room dynamics, because its hard to give good advice without being in the room. very, very, few people have a perfectly planned out audio room, and if you are going to argue that another sub in pair will give you a flatter response, then why just stop at 2, you can get 4 and get even more of a flat response. you will get better performance from one better sub and a powered sub for each channel then you ever would from 2 lesser subs. that is why a lot of companies have powered towers everywhere, its just that the powered part of the tower is typically pretty bad. i would always buy one better sub than two lesser ones, unless i had an absolutely horrible acoustically neutral room. if i was thinking of adding some subs to complement one such as he has, i would not do so by buying one to put in pair with it, i would buy something along the lines of what i said previously. you can always spend more money on something, but that doesnt mean it is worth the money to do so, and you can spend a ton on audio, so i try to think of things in a cost effective sense. youd be happier buying two subs that cost the price of one and putting them up at the front, than putting the one in pair. that DOES NOT APPLY to the lfe sub though (as i stated above, one good is better than two bad), but when you are localizing the bass to a speaker its not as vital. i mean ideally youd put the best subs at all channels and lfe, but money is always a factor.... :-)