Subwoofers driving me nuts

I can't hear the issue, that's the problem, right?  You have any room treatment, at all?  If you could get your position closer to a back wall, then treat the wall behind you. Normally  further from the speakers, the deeper the bass, to a point. Speakers 4-8 foot from (their) rear wall, 2-4 ft. from sides. Your position 8-12" from mains and 4 feet from your BACK, not the middle of the room.
French doors, sound like a bad idea, until they are opened on a back wall, behind the listening position. 
The BASS, escapes, not reflects. The wall behind the speakers is very, important, every wall has an issue, the more you can tame (or get rid of), the more you can hear.  If you can't kill let the sound escape, you have to use it, "reflex bass".
The only thing left at that point is measure and EQ, HUGE bumps, and that will take care of some of the NULLS. Then EQ up to where you need. In the setting position. If your trying to get bass on a dance floor, that's different too, four TOP corners, pointing down on the floor. or NO BASS.

If you can;  mains at 40-60hz and above, subs go from there down. THEN you'll probably start to hear more than one note, and bass.
Most people have their subs set WAY to high, Sub is actually what you CAN'T hear only feel. SUB.. You got to much of a GOOD thing.. I'm at 50 hz and down on two subs, and 35-40 hz and down on the others (2-4). ALL are cut at 20 and below. (glass is expensive).

Regards

Since the swarm-is-the-rage, I'm wondering how this config would sound: A 15-18 sub (single) in the middle, two 12s (left and right), and two 8-10s (further left and right). Another reason to play the lottery!

In my 28 year listening experience, I've never used more than one sub. I'm currently using a 20 year-old B&W ASW650 (lit says 12 inch but more 10-11 inch) in my smaller room (12 X 13). Listened to Joni Mitchell's intro to "Cotton Avenue" recently and Jaco's bass was "all there" which is good enough for me. 

Good luck with you project! 

Miller, thanks for the idea.  I've been struggling to get my two subs correct and I moved one  down the side wall almost to my position, adjusted the delay and when I adjusted phase on the odd one to 120 degree to account for distance it just clicked. They vanished and I can not locate them. I would have never thought of placing them in an unrelated position.  Much obliged....