Dual subs and room size

While we're on this subject, I have a question. Did I read someplace that newer stereo releases are being mix/mastered for separation down to 20Hz (and below)? Would this be a good reason to go for two subs?

There are several industry experts which will only recommend 2 subs in a 2 channel system.  George Vandersteen and Jim Smith to name a couple.  To the point they state, for a 2 channel system,  they would not add a sub to the system until they had 2.  In my own experience,  I owned a single JL Audio F212, and I was never able to get it to blend right with my speakers,  and I felt it took away from the imaging of the main speakers.  It wasnt,  due to lack of trying, I worked for weeks on sub placement and in different rooms with different speakers,  B&W 802D2,  Revel Salon 2,  Aerial Acoustics 20T V2.  Rooms all treated.  After researching,  ultimately bought a second F212 and was blow away by the improvement.   In fact,  I didn't tell my wife I bought the second sub and was playing the system, she said,  "wow,  that is sounding really good".  What did you change?"

Corrcting myself.  It is Richard Vandersteen, not George.  

X2 karm same experience. And i just love those f112 . Pricey but it shows

Again I want to thank you for your advice and guidance, I have been following your leads. Last night I spent some time moving and adjusting my current ML orig model Dynamo sub. Wow what difference. Will continue to lock it and conduct measurements. Will be ordering one sub with a thought to two after I lock that one in. Very interesting process. Dave